Source code for jax._src.api

# Copyright 2018 The JAX Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""JAX user-facing transformations and utilities.

The transformations here mostly wrap internal transformations, providing
convenience flags to control behavior and handling Python containers of
arguments and outputs. The Python containers handled are pytrees (see
tree_util.py), which include nested tuples/lists/dicts, where the leaves are
arrays.
"""
from __future__ import annotations

import collections
from collections.abc import Generator, Hashable, Iterable, Sequence
from functools import partial
import inspect
import math
import typing
from typing import (Any, Callable, Literal, NamedTuple, TypeVar, overload,
                    cast)
import weakref

import numpy as np
from contextlib import contextmanager, ExitStack

from jax._src import linear_util as lu
from jax._src import stages
from jax._src.tree_util import (
    tree_map, tree_flatten, tree_unflatten, tree_structure, tree_transpose,
    tree_leaves, Partial, PyTreeDef, all_leaves, keystr, broadcast_prefix,
    prefix_errors, generate_key_paths)
from jax._src import api_util
from jax._src import config
from jax._src import core
from jax._src import dispatch
from jax._src import effects
from jax._src import array
from jax._src import basearray
from jax._src import dtypes
from jax._src import sharding_impls
from jax._src import sharding_specs
from jax._src import source_info_util
from jax._src import traceback_util
from jax._src import pjit
from jax._src import xla_bridge as xb
from jax._src.core import eval_jaxpr, ShapedArray, ConcreteArray
from jax._src.api_util import (
    flatten_fun, flatten_fun_nokwargs, flatten_fun_nokwargs2, argnums_partial,
    argnums_partial_except, flatten_axes, donation_vector,
    rebase_donate_argnums, _ensure_index, _ensure_index_tuple,
    shaped_abstractify, apply_flat_fun_nokwargs, check_callable, debug_info,
    result_paths, flat_out_axes, debug_info_final, fun_sourceinfo)
from jax._src.lax import lax as lax_internal
from jax._src.lib import jax_jit
from jax._src.lib import xla_client as xc
from jax._src.lib import xla_extension_version
from jax._src.lib import pmap_lib
from jax._src.sharding import Sharding
from jax._src.sharding_impls import (PmapSharding, TransferToMemoryKind,
                                     XLACompatibleSharding)
from jax._src.traceback_util import api_boundary
from jax._src import tree_util
from jax._src.util import unzip2, safe_map, safe_zip, wrap_name, wraps
from jax._src import util

from jax._src.interpreters import ad
from jax._src.interpreters import batching
from jax._src.interpreters import mlir
from jax._src.interpreters import partial_eval as pe
from jax._src.interpreters import pxla
from jax._src.interpreters import xla


traceback_util.register_exclusion(__file__)

_dtype = partial(dtypes.dtype, canonicalize=True)

AxisName = Hashable

Device = xc.Device

# These TypeVars are used below to express the fact that function types
# (i.e. call signatures) are invariant under the vmap transformation.
F = TypeVar("F", bound=Callable)
T = TypeVar("T")
U = TypeVar("U")

map, unsafe_map = safe_map, map
zip, unsafe_zip = safe_zip, zip


def _nan_check_posthook(fun, args, kwargs, output):
  """Hook function called by the C++ jit/pmap to perform NaN checking."""
  buffers = []
  for leaf in tree_leaves(output):
    if hasattr(leaf, "addressable_shards"):
      buffers.extend([shard.data for shard in leaf.addressable_shards])

  try:
    dispatch.check_special(pjit.pjit_p.name, buffers)
  except FloatingPointError:
    # compiled_fun can only raise in this case
    assert config.debug_nans.value or config.debug_infs.value
    print("Invalid nan value encountered in the output of a C++-jit/pmap "
          "function. Calling the de-optimized version.")
    fun._cache_miss(*args, **kwargs)[0]  # probably won't return

def _update_debug_special_global(_):
  if config._read("jax_debug_nans") or config._read("jax_debug_infs"):
    jax_jit.global_state().post_hook = _nan_check_posthook
  else:
    jax_jit.global_state().post_hook = None

def _update_debug_special_thread_local(_):
  if (getattr(config._thread_local_state, "jax_debug_nans", False) or
      getattr(config._thread_local_state, "jax_debug_infs", False)):
    jax_jit.thread_local_state().post_hook = _nan_check_posthook
  else:
    jax_jit.thread_local_state().post_hook = None

config.debug_nans._add_hooks(_update_debug_special_global,
                             _update_debug_special_thread_local)
config.debug_infs._add_hooks(_update_debug_special_global,
                             _update_debug_special_thread_local)


float0 = dtypes.float0


[docs] def jit( fun: Callable, in_shardings=sharding_impls.UNSPECIFIED, out_shardings=sharding_impls.UNSPECIFIED, static_argnums: int | Sequence[int] | None = None, static_argnames: str | Iterable[str] | None = None, donate_argnums: int | Sequence[int] | None = None, donate_argnames: str | Iterable[str] | None = None, keep_unused: bool = False, device: xc.Device | None = None, backend: str | None = None, inline: bool = False, abstracted_axes: Any | None = None, ) -> pjit.JitWrapped: """Sets up ``fun`` for just-in-time compilation with XLA. Args: fun: Function to be jitted. ``fun`` should be a pure function, as side-effects may only be executed once. The arguments and return value of ``fun`` should be arrays, scalars, or (nested) standard Python containers (tuple/list/dict) thereof. Positional arguments indicated by ``static_argnums`` can be anything at all, provided they are hashable and have an equality operation defined. Static arguments are included as part of a compilation cache key, which is why hash and equality operators must be defined. JAX keeps a weak reference to ``fun`` for use as a compilation cache key, so the object ``fun`` must be weakly-referenceable. Most :class:`Callable` objects will already satisfy this requirement. in_shardings: Pytree of structure matching that of arguments to ``fun``, with all actual arguments replaced by resource assignment specifications. It is also valid to specify a pytree prefix (e.g. one value in place of a whole subtree), in which case the leaves get broadcast to all values in that subtree. The ``in_shardings`` argument is optional. JAX will infer the shardings from the input :py:class:`jax.Array`'s and defaults to replicating the input if the sharding cannot be inferred. The valid resource assignment specifications are: - :py:class:`XLACompatibleSharding`, which will decide how the value will be partitioned. With this, using a mesh context manager is not required. - :py:obj:`None`, will give JAX the freedom to choose whatever sharding it wants. For in_shardings, JAX will mark is as replicated but this behavior can change in the future. For out_shardings, we will rely on the XLA GSPMD partitioner to determine the output shardings. The size of every dimension has to be a multiple of the total number of resources assigned to it. This is similar to pjit's in_shardings. out_shardings: Like ``in_shardings``, but specifies resource assignment for function outputs. This is similar to pjit's out_shardings. The ``out_shardings`` argument is optional. If not specified, :py:func:`jax.jit` will use GSPMD's sharding propagation to figure out what the sharding of the output(s) should be. static_argnums: An optional int or collection of ints that specify which positional arguments to treat as static (compile-time constant). Operations that only depend on static arguments will be constant-folded in Python (during tracing), and so the corresponding argument values can be any Python object. Static arguments should be hashable, meaning both ``__hash__`` and ``__eq__`` are implemented, and immutable. Calling the jitted function with different values for these constants will trigger recompilation. Arguments that are not arrays or containers thereof must be marked as static. If neither ``static_argnums`` nor ``static_argnames`` is provided, no arguments are treated as static. If ``static_argnums`` is not provided but ``static_argnames`` is, or vice versa, JAX uses :code:`inspect.signature(fun)` to find any positional arguments that correspond to ``static_argnames`` (or vice versa). If both ``static_argnums`` and ``static_argnames`` are provided, ``inspect.signature`` is not used, and only actual parameters listed in either ``static_argnums`` or ``static_argnames`` will be treated as static. static_argnames: An optional string or collection of strings specifying which named arguments to treat as static (compile-time constant). See the comment on ``static_argnums`` for details. If not provided but ``static_argnums`` is set, the default is based on calling ``inspect.signature(fun)`` to find corresponding named arguments. donate_argnums: Specify which positional argument buffers are "donated" to the computation. It is safe to donate argument buffers if you no longer need them once the computation has finished. In some cases XLA can make use of donated buffers to reduce the amount of memory needed to perform a computation, for example recycling one of your input buffers to store a result. You should not reuse buffers that you donate to a computation, JAX will raise an error if you try to. By default, no argument buffers are donated. If neither ``donate_argnums`` nor ``donate_argnames`` is provided, no arguments are donated. If ``donate_argnums`` is not provided but ``donate_argnames`` is, or vice versa, JAX uses :code:`inspect.signature(fun)` to find any positional arguments that correspond to ``donate_argnames`` (or vice versa). If both ``donate_argnums`` and ``donate_argnames`` are provided, ``inspect.signature`` is not used, and only actual parameters listed in either ``donate_argnums`` or ``donate_argnames`` will be donated. For more details on buffer donation see the `FAQ <https://jax.readthedocs.io/en/latest/faq.html#buffer-donation>`_. donate_argnames: An optional string or collection of strings specifying which named arguments are donated to the computation. See the comment on ``donate_argnums`` for details. If not provided but ``donate_argnums`` is set, the default is based on calling ``inspect.signature(fun)`` to find corresponding named arguments. keep_unused: If `False` (the default), arguments that JAX determines to be unused by `fun` *may* be dropped from resulting compiled XLA executables. Such arguments will not be transferred to the device nor provided to the underlying executable. If `True`, unused arguments will not be pruned. device: This is an experimental feature and the API is likely to change. Optional, the Device the jitted function will run on. (Available devices can be retrieved via :py:func:`jax.devices`.) The default is inherited from XLA's DeviceAssignment logic and is usually to use ``jax.devices()[0]``. backend: This is an experimental feature and the API is likely to change. Optional, a string representing the XLA backend: ``'cpu'``, ``'gpu'``, or ``'tpu'``. inline: Specify whether this function should be inlined into enclosing jaxprs (rather than being represented as an application of the xla_call primitive with its own subjaxpr). Default False. Returns: A wrapped version of ``fun``, set up for just-in-time compilation. Examples: In the following example, ``selu`` can be compiled into a single fused kernel by XLA: >>> import jax >>> >>> @jax.jit ... def selu(x, alpha=1.67, lmbda=1.05): ... return lmbda * jax.numpy.where(x > 0, x, alpha * jax.numpy.exp(x) - alpha) >>> >>> key = jax.random.PRNGKey(0) >>> x = jax.random.normal(key, (10,)) >>> print(selu(x)) # doctest: +SKIP [-0.54485 0.27744 -0.29255 -0.91421 -0.62452 -0.24748 -0.85743 -0.78232 0.76827 0.59566 ] To pass arguments such as ``static_argnames`` when decorating a function, a common pattern is to use :func:`functools.partial`: >>> from functools import partial >>> >>> @partial(jax.jit, static_argnames=['n']) ... def g(x, n): ... for i in range(n): ... x = x ** 2 ... return x >>> >>> g(jnp.arange(4), 3) Array([ 0, 1, 256, 6561], dtype=int32) """ (in_shardings, out_shardings, donate_argnums, donate_argnames, static_argnums, static_argnames) = pjit.pre_infer_params( fun, in_shardings, out_shardings, donate_argnums, donate_argnames, static_argnums, static_argnames, device, backend, abstracted_axes) fun_sourceinfo = api_util.fun_sourceinfo(fun) fun_signature = api_util.fun_signature(fun) def infer_params(*args, **kwargs): # TODO(yashkatariya): Remove this when it's added on jit. in_layouts = kwargs.pop('_in_layouts', None) out_layouts = kwargs.pop('_out_layouts', None) pjit_info_args = pjit.PjitInfo( fun=fun, fun_sourceinfo=fun_sourceinfo, fun_signature=fun_signature, in_shardings=in_shardings, out_shardings=out_shardings, static_argnums=static_argnums, static_argnames=static_argnames, donate_argnums=donate_argnums, donate_argnames=donate_argnames, device=device, backend=backend, keep_unused=keep_unused, inline=inline, resource_env=None, abstracted_axes=abstracted_axes, in_layouts=in_layouts, out_layouts=out_layouts) return pjit.common_infer_params(pjit_info_args, *args, **kwargs) has_explicit_sharding = pjit._pjit_explicit_sharding( in_shardings, out_shardings, device, backend) return pjit.post_infer_params(fun, infer_params, static_argnums, static_argnames, donate_argnums, abstracted_axes, has_explicit_sharding)
[docs] @contextmanager def disable_jit(disable: bool = True): """Context manager that disables :py:func:`jit` behavior under its dynamic context. For debugging it is useful to have a mechanism that disables :py:func:`jit` everywhere in a dynamic context. Note that this not only disables explicit uses of :func:`jit` by the user, but will also remove any implicit JIT compilation used by the JAX library: this includes implicit JIT computation of `body` and `cond` functions passed to higher-level primitives like :func:`~jax.lax.scan` and :func:`~jax.lax.while_loop`, JIT used in implementations of :mod:`jax.numpy` functions, and any other case where :func:`jit` is used within an API's implementation. Note however that even under `disable_jit`, individual primitive operations will still be compiled by XLA as in normal eager op-by-op execution. Values that have a data dependence on the arguments to a jitted function are traced and abstracted. For example, an abstract value may be a :py:class:`ShapedArray` instance, representing the set of all possible arrays with a given shape and dtype, but not representing one concrete array with specific values. You might notice those if you use a benign side-effecting operation in a jitted function, like a print: >>> import jax >>> >>> @jax.jit ... def f(x): ... y = x * 2 ... print("Value of y is", y) ... return y + 3 ... >>> print(f(jax.numpy.array([1, 2, 3]))) # doctest:+ELLIPSIS Value of y is Traced<ShapedArray(int32[3])>with<DynamicJaxprTrace...> [5 7 9] Here ``y`` has been abstracted by :py:func:`jit` to a :py:class:`ShapedArray`, which represents an array with a fixed shape and type but an arbitrary value. The value of ``y`` is also traced. If we want to see a concrete value while debugging, and avoid the tracer too, we can use the :py:func:`disable_jit` context manager: >>> import jax >>> >>> with jax.disable_jit(): ... print(f(jax.numpy.array([1, 2, 3]))) ... Value of y is [2 4 6] [5 7 9] """ with config.disable_jit(disable): yield
[docs] def xla_computation(fun: Callable, static_argnums: int | Iterable[int] = (), axis_env: Sequence[tuple[AxisName, int]] | None = None, in_parts=None, out_parts=None, backend: str | None = None, tuple_args: bool = False, instantiate_const_outputs: bool | None = None, return_shape: bool = False, donate_argnums: int | Iterable[int] = ()) -> Callable: """Creates a function that produces its XLA computation given example args. Args: fun: Function from which to form XLA computations. static_argnums: See the :py:func:`jax.jit` docstring. axis_env: Optional, a sequence of pairs where the first element is an axis name and the second element is a positive integer representing the size of the mapped axis with that name. This parameter is useful when lowering functions that involve parallel communication collectives, and it specifies the axis name/size environment that would be set up by applications of :py:func:`jax.pmap`. See the examples below. in_parts: Optional, how each argument to ``fun`` should be partitioned or replicated. This is used to specify partitioned XLA computations, see ``sharded_jit`` for more info. out_parts: Optional, how each output of ``fun`` should be partitioned or replicated. This is used to specify partitioned XLA computations, see ``sharded_jit`` for more info. backend: This is an experimental feature and the API is likely to change. Optional, a string representing the XLA backend: ``'cpu'``, ``'gpu'``, or ``'tpu'``. tuple_args: Optional bool, defaults to ``False``. If ``True``, the resulting XLA computation will have a single tuple argument that is unpacked into the specified function arguments. If `None`, tupling will be enabled when there are more than 100 arguments, since some platforms have limits on argument arity. instantiate_const_outputs: Deprecated argument, does nothing. return_shape: Optional boolean, defaults to ``False``. If ``True``, the wrapped function returns a pair where the first element is the XLA computation and the second element is a pytree with the same structure as the output of ``fun`` and where the leaves are objects with ``shape``, ``dtype``, and ``named_shape`` attributes representing the corresponding types of the output leaves. donate_argnums: Specify which arguments are "donated" to the computation. It is safe to donate arguments if you no longer need them once the computation has finished. In some cases XLA can make use of donated buffers to reduce the amount of memory needed to perform a computation, for example recycling one of your input buffers to store a result. You should not reuse buffers that you donate to a computation, JAX will raise an error if you try to. Returns: A wrapped version of ``fun`` that when applied to example arguments returns a built XLA Computation (see xla_client.py), from which representations of the unoptimized XLA HLO computation can be extracted using methods like ``as_hlo_text``, ``as_serialized_hlo_module_proto``, and ``as_hlo_dot_graph``. If the argument ``return_shape`` is ``True``, then the wrapped function returns a pair where the first element is the XLA Computation and the second element is a pytree representing the structure, shapes, dtypes, and named shapes of the output of ``fun``. Concrete example arguments are not always necessary. For those arguments not indicated by ``static_argnums``, any object with ``shape`` and ``dtype`` attributes is acceptable (excepting namedtuples, which are treated as Python containers). For example: >>> import jax >>> >>> def f(x): return jax.numpy.sin(jax.numpy.cos(x)) >>> c = jax.xla_computation(f)(3.) >>> print(c.as_hlo_text()) # doctest: +SKIP HloModule xla_computation_f.6 <BLANKLINE> ENTRY xla_computation_f.6 { constant.2 = pred[] constant(false) parameter.1 = f32[] parameter(0) cosine.3 = f32[] cosine(parameter.1) sine.4 = f32[] sine(cosine.3) ROOT tuple.5 = (f32[]) tuple(sine.4) } <BLANKLINE> <BLANKLINE> Alternatively, the assignment to ``c`` above could be written: >>> import types >>> scalar = types.SimpleNamespace(shape=(), dtype=np.dtype(np.float32)) >>> c = jax.xla_computation(f)(scalar) Here's an example that involves a parallel collective and axis name: >>> def f(x): return x - jax.lax.psum(x, 'i') >>> c = jax.xla_computation(f, axis_env=[('i', 4)])(2) >>> print(c.as_hlo_text()) # doctest: +SKIP HloModule jaxpr_computation.9 primitive_computation.3 { parameter.4 = s32[] parameter(0) parameter.5 = s32[] parameter(1) ROOT add.6 = s32[] add(parameter.4, parameter.5) } ENTRY jaxpr_computation.9 { tuple.1 = () tuple() parameter.2 = s32[] parameter(0) all-reduce.7 = s32[] all-reduce(parameter.2), replica_groups={{0,1,2,3}}, to_apply=primitive_computation.3 ROOT subtract.8 = s32[] subtract(parameter.2, all-reduce.7) } <BLANKLINE> <BLANKLINE> Notice the ``replica_groups`` that were generated. Here's an example that generates more interesting ``replica_groups``: >>> from jax import lax >>> def g(x): ... rowsum = lax.psum(x, 'i') ... colsum = lax.psum(x, 'j') ... allsum = lax.psum(x, ('i', 'j')) ... return rowsum, colsum, allsum ... >>> axis_env = [('i', 4), ('j', 2)] >>> c = xla_computation(g, axis_env=axis_env)(5.) >>> print(c.as_hlo_text()) # doctest: +SKIP HloModule jaxpr_computation__1.19 [removed uninteresting text here] ENTRY jaxpr_computation__1.19 { tuple.1 = () tuple() parameter.2 = f32[] parameter(0) all-reduce.7 = f32[] all-reduce(parameter.2), replica_groups={{0,2,4,6},{1,3,5,7}}, to_apply=primitive_computation__1.3 all-reduce.12 = f32[] all-reduce(parameter.2), replica_groups={{0,1},{2,3},{4,5},{6,7}}, to_apply=primitive_computation__1.8 all-reduce.17 = f32[] all-reduce(parameter.2), replica_groups={{0,1,2,3,4,5,6,7}}, to_apply=primitive_computation__1.13 ROOT tuple.18 = (f32[], f32[], f32[]) tuple(all-reduce.7, all-reduce.12, all-reduce.17) } """ if instantiate_const_outputs is not None: raise ValueError( "instantiate_const_outputs has been deprecated. Please use the ahead of" " time APIs. You can read more here:" " https://jax.readthedocs.io/en/latest/aot.html") if in_parts is not None: raise ValueError( "in_parts has been deprecated. Please use the ahead of time APIs. You" " can read more here: https://jax.readthedocs.io/en/latest/aot.html") if out_parts is not None: raise ValueError( "out_parts has been deprecated. Please use the ahead of time APIs. You" " can read more here: https://jax.readthedocs.io/en/latest/aot.html") check_callable(fun) static_argnums = _ensure_index_tuple(static_argnums) donate_argnums = _ensure_index_tuple(donate_argnums) donate_argnums = rebase_donate_argnums(donate_argnums, static_argnums) fun_name = getattr(fun, "__name__", "unknown") platform = backend if backend is not None else xb.get_backend().platform def make_axis_env(nreps): if axis_env is None: return sharding_impls.AxisEnv(nreps, (), ()) else: nreps = nreps * math.prod(size for name, size in axis_env) names, sizes = unzip2(axis_env) return sharding_impls.AxisEnv(nreps, names, sizes) @wraps(fun) @api_boundary def computation_maker(*args, **kwargs): if max(static_argnums + donate_argnums, default=-1) >= len(args): raise ValueError(f"jitted function has {static_argnums=}, {donate_argnums=} but " f"was called with only {len(args)} positional arguments.") f = lu.wrap_init(fun) f, dyn_args = argnums_partial_except(f, static_argnums, args, allow_invalid=False) args_flat, in_tree = tree_flatten((dyn_args, kwargs)) if donate_argnums: donated_invars = donation_vector(donate_argnums, (), dyn_args, kwargs) else: donated_invars = (False,) * len(args_flat) jaxtree_fun, out_tree = flatten_fun(f, in_tree) avals = map(shaped_abstractify, args_flat) with ExitStack() as stack: for axis_name, size in axis_env or []: stack.enter_context(core.extend_axis_env(axis_name, size, None)) jaxpr, out_avals, consts, () = pe.trace_to_jaxpr_dynamic(jaxtree_fun, avals) jaxpr = dispatch.apply_outfeed_rewriter(jaxpr) axis_env_ = make_axis_env(dispatch.jaxpr_replicas(jaxpr)) ordered_effects = list( effects.ordered_effects.filter_in(jaxpr.effects)) lowering_result = mlir.lower_jaxpr_to_module( f"xla_computation_{fun_name}", core.ClosedJaxpr(jaxpr, consts), ordered_effects=ordered_effects, backend_or_name=backend, platforms=[platform], axis_context=sharding_impls.ReplicaAxisContext(axis_env_), name_stack=source_info_util.new_name_stack( wrap_name(fun_name, "xla_computation")), donated_args=donated_invars, arg_shardings=None, result_shardings=None, lowering_parameters=mlir.LoweringParameters()) built = xc._xla.mlir.mlir_module_to_xla_computation( mlir.module_to_string(lowering_result.module), use_tuple_args=tuple_args, return_tuple=True) out_shapes_flat = [ ShapeDtypeStruct(a.shape, a.dtype, a.named_shape) for a in out_avals] out_shape = tree_unflatten(out_tree(), out_shapes_flat) for out_aval in out_avals: if not isinstance(out_aval, ShapedArray): raise RuntimeError("As we want to propagate the weak_type, we need " "to get a ShapedArray, otherwise this " "information is lost") if return_shape: return built, out_shape else: return built return computation_maker
[docs] def grad(fun: Callable, argnums: int | Sequence[int] = 0, has_aux: bool = False, holomorphic: bool = False, allow_int: bool = False, reduce_axes: Sequence[AxisName] = ()) -> Callable: """Creates a function that evaluates the gradient of ``fun``. Args: fun: Function to be differentiated. Its arguments at positions specified by ``argnums`` should be arrays, scalars, or standard Python containers. Argument arrays in the positions specified by ``argnums`` must be of inexact (i.e., floating-point or complex) type. It should return a scalar (which includes arrays with shape ``()`` but not arrays with shape ``(1,)`` etc.) argnums: Optional, integer or sequence of integers. Specifies which positional argument(s) to differentiate with respect to (default 0). has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. holomorphic: Optional, bool. Indicates whether ``fun`` is promised to be holomorphic. If True, inputs and outputs must be complex. Default False. allow_int: Optional, bool. Whether to allow differentiating with respect to integer valued inputs. The gradient of an integer input will have a trivial vector-space dtype (float0). Default False. Returns: A function with the same arguments as ``fun``, that evaluates the gradient of ``fun``. If ``argnums`` is an integer then the gradient has the same shape and type as the positional argument indicated by that integer. If argnums is a tuple of integers, the gradient is a tuple of values with the same shapes and types as the corresponding arguments. If ``has_aux`` is True then a pair of (gradient, auxiliary_data) is returned. For example: >>> import jax >>> >>> grad_tanh = jax.grad(jax.numpy.tanh) >>> print(grad_tanh(0.2)) 0.961043 """ if reduce_axes: raise NotImplementedError("reduce_axes argument to grad is deprecated") del reduce_axes value_and_grad_f = value_and_grad(fun, argnums, has_aux=has_aux, holomorphic=holomorphic, allow_int=allow_int) docstr = ("Gradient of {fun} with respect to positional argument(s) " "{argnums}. Takes the same arguments as {fun} but returns the " "gradient, which has the same shape as the arguments at " "positions {argnums}.") @wraps(fun, docstr=docstr, argnums=argnums) @api_boundary def grad_f(*args, **kwargs): _, g = value_and_grad_f(*args, **kwargs) return g @wraps(fun, docstr=docstr, argnums=argnums) @api_boundary def grad_f_aux(*args, **kwargs): (_, aux), g = value_and_grad_f(*args, **kwargs) return g, aux return grad_f_aux if has_aux else grad_f
[docs] def value_and_grad(fun: Callable, argnums: int | Sequence[int] = 0, has_aux: bool = False, holomorphic: bool = False, allow_int: bool = False, reduce_axes: Sequence[AxisName] = () ) -> Callable[..., tuple[Any, Any]]: """Create a function that evaluates both ``fun`` and the gradient of ``fun``. Args: fun: Function to be differentiated. Its arguments at positions specified by ``argnums`` should be arrays, scalars, or standard Python containers. It should return a scalar (which includes arrays with shape ``()`` but not arrays with shape ``(1,)`` etc.) argnums: Optional, integer or sequence of integers. Specifies which positional argument(s) to differentiate with respect to (default 0). has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. holomorphic: Optional, bool. Indicates whether ``fun`` is promised to be holomorphic. If True, inputs and outputs must be complex. Default False. allow_int: Optional, bool. Whether to allow differentiating with respect to integer valued inputs. The gradient of an integer input will have a trivial vector-space dtype (float0). Default False. Returns: A function with the same arguments as ``fun`` that evaluates both ``fun`` and the gradient of ``fun`` and returns them as a pair (a two-element tuple). If ``argnums`` is an integer then the gradient has the same shape and type as the positional argument indicated by that integer. If argnums is a sequence of integers, the gradient is a tuple of values with the same shapes and types as the corresponding arguments. If ``has_aux`` is True then a tuple of ((value, auxiliary_data), gradient) is returned. """ if reduce_axes: raise NotImplementedError("reduce_axes argument to grad is deprecated") del reduce_axes docstr = ("Value and gradient of {fun} with respect to positional " "argument(s) {argnums}. Takes the same arguments as {fun} but " "returns a two-element tuple where the first element is the value " "of {fun} and the second element is the gradient, which has the " "same shape as the arguments at positions {argnums}.") check_callable(fun) argnums = core.concrete_or_error(_ensure_index, argnums) @wraps(fun, docstr=docstr, argnums=argnums) @api_boundary def value_and_grad_f(*args, **kwargs): max_argnum = argnums if isinstance(argnums, int) else max(argnums) if max_argnum >= len(args): raise TypeError(f"differentiating with respect to {argnums=} requires at least " f"{max_argnum + 1} positional arguments to be passed by the caller, " f"but got only {len(args)} positional arguments.") f = lu.wrap_init(fun, kwargs) f_partial, dyn_args = argnums_partial(f, argnums, args, require_static_args_hashable=False) for leaf in tree_leaves(dyn_args): _check_input_dtype_grad(holomorphic, allow_int, leaf) if not has_aux: ans, vjp_py = _vjp(f_partial, *dyn_args) else: ans, vjp_py, aux = _vjp( f_partial, *dyn_args, has_aux=True) _check_scalar(ans) tree_map(partial(_check_output_dtype_grad, holomorphic), ans) g = vjp_py(lax_internal._one(ans)) g = g[0] if isinstance(argnums, int) else g if not has_aux: return ans, g else: return (ans, aux), g return value_and_grad_f
def _check_scalar(x): msg = "Gradient only defined for scalar-output functions. Output {}.".format try: aval = core.get_aval(x) except TypeError as e: raise TypeError(msg(f"was {x}")) from e else: if isinstance(aval, ShapedArray): if aval.shape != (): raise TypeError(msg(f"had shape: {aval.shape}")) else: raise TypeError(msg(f"had abstract value {aval}")) def _check_input_dtype_revderiv(name, holomorphic, allow_int, x): dispatch.check_arg(x) aval = core.get_aval(x) if holomorphic: if not dtypes.issubdtype(aval.dtype, np.complexfloating): raise TypeError(f"{name} with holomorphic=True requires inputs with complex dtype, " f"but got {aval.dtype.name}.") if (dtypes.issubdtype(aval.dtype, dtypes.extended) or dtypes.issubdtype(aval.dtype, np.integer) or dtypes.issubdtype(aval.dtype, np.bool_)): if not allow_int: raise TypeError(f"{name} requires real- or complex-valued inputs (input dtype " f"that is a sub-dtype of np.inexact), but got {aval.dtype.name}. " "If you want to use Boolean- or integer-valued inputs, use vjp " "or set allow_int to True.") elif not dtypes.issubdtype(aval.dtype, np.inexact): raise TypeError(f"{name} requires numerical-valued inputs (input dtype that is a " f"sub-dtype of np.bool_ or np.number), but got {aval.dtype.name}.") _check_input_dtype_grad = partial(_check_input_dtype_revderiv, "grad") def _check_output_dtype_revderiv(name, holomorphic, x): aval = core.get_aval(x) if dtypes.issubdtype(aval.dtype, dtypes.extended): raise TypeError( f"{name} with output element type {aval.dtype.name}") if holomorphic: if not dtypes.issubdtype(aval.dtype, np.complexfloating): raise TypeError(f"{name} with holomorphic=True requires outputs with complex dtype, " f"but got {aval.dtype.name}.") elif dtypes.issubdtype(aval.dtype, np.complexfloating): raise TypeError(f"{name} requires real-valued outputs (output dtype that is " f"a sub-dtype of np.floating), but got {aval.dtype.name}. " "For holomorphic differentiation, pass holomorphic=True. " "For differentiation of non-holomorphic functions involving complex " "outputs, use jax.vjp directly.") elif not dtypes.issubdtype(aval.dtype, np.floating): raise TypeError(f"{name} requires real-valued outputs (output dtype that is " f"a sub-dtype of np.floating), but got {aval.dtype.name}. " "For differentiation of functions with integer outputs, use " "jax.vjp directly.") _check_output_dtype_grad = partial(_check_output_dtype_revderiv, "grad")
[docs] def jacfwd(fun: Callable, argnums: int | Sequence[int] = 0, has_aux: bool = False, holomorphic: bool = False) -> Callable: """Jacobian of ``fun`` evaluated column-by-column using forward-mode AD. Args: fun: Function whose Jacobian is to be computed. argnums: Optional, integer or sequence of integers. Specifies which positional argument(s) to differentiate with respect to (default ``0``). has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. holomorphic: Optional, bool. Indicates whether ``fun`` is promised to be holomorphic. Default False. Returns: A function with the same arguments as ``fun``, that evaluates the Jacobian of ``fun`` using forward-mode automatic differentiation. If ``has_aux`` is True then a pair of (jacobian, auxiliary_data) is returned. >>> import jax >>> import jax.numpy as jnp >>> >>> def f(x): ... return jnp.asarray( ... [x[0], 5*x[2], 4*x[1]**2 - 2*x[2], x[2] * jnp.sin(x[0])]) ... >>> print(jax.jacfwd(f)(jnp.array([1., 2., 3.]))) [[ 1. 0. 0. ] [ 0. 0. 5. ] [ 0. 16. -2. ] [ 1.6209 0. 0.84147]] """ check_callable(fun) argnums = _ensure_index(argnums) docstr = ("Jacobian of {fun} with respect to positional argument(s) " "{argnums}. Takes the same arguments as {fun} but returns the " "jacobian of the output with respect to the arguments at " "positions {argnums}.") @wraps(fun, docstr=docstr, argnums=argnums) def jacfun(*args, **kwargs): f = lu.wrap_init(fun, kwargs) f_partial, dyn_args = argnums_partial(f, argnums, args, require_static_args_hashable=False) tree_map(partial(_check_input_dtype_jacfwd, holomorphic), dyn_args) if not has_aux: pushfwd: Callable = partial(_jvp, f_partial, dyn_args) y, jac = vmap(pushfwd, out_axes=(None, -1))(_std_basis(dyn_args)) else: pushfwd: Callable = partial(_jvp, f_partial, dyn_args, has_aux=True) y, jac, aux = vmap(pushfwd, out_axes=(None, -1, None))(_std_basis(dyn_args)) tree_map(partial(_check_output_dtype_jacfwd, holomorphic), y) example_args = dyn_args[0] if isinstance(argnums, int) else dyn_args jac_tree = tree_map(partial(_jacfwd_unravel, example_args), y, jac) if not has_aux: return jac_tree else: return jac_tree, aux return jacfun
def _check_input_dtype_jacfwd(holomorphic: bool, x: Any) -> None: dispatch.check_arg(x) aval = core.get_aval(x) if dtypes.issubdtype(aval.dtype, dtypes.extended): raise TypeError( f"jacfwd with input element type {aval.dtype.name}") if holomorphic: if not dtypes.issubdtype(aval.dtype, np.complexfloating): raise TypeError("jacfwd with holomorphic=True requires inputs with complex " f"dtype, but got {aval.dtype.name}.") elif not dtypes.issubdtype(aval.dtype, np.floating): raise TypeError("jacfwd requires real-valued inputs (input dtype that is " f"a sub-dtype of np.floating), but got {aval.dtype.name}. " "For holomorphic differentiation, pass holomorphic=True. " "For differentiation of non-holomorphic functions involving " "complex inputs or integer inputs, use jax.jvp directly.") def _check_output_dtype_jacfwd(holomorphic, x): aval = core.get_aval(x) if holomorphic: if not dtypes.issubdtype(aval.dtype, np.complexfloating): raise TypeError("jacfwd with holomorphic=True requires outputs with complex dtype, " f"but got {aval.dtype.name}.")
[docs] def jacrev(fun: Callable, argnums: int | Sequence[int] = 0, has_aux: bool = False, holomorphic: bool = False, allow_int: bool = False) -> Callable: """Jacobian of ``fun`` evaluated row-by-row using reverse-mode AD. Args: fun: Function whose Jacobian is to be computed. argnums: Optional, integer or sequence of integers. Specifies which positional argument(s) to differentiate with respect to (default ``0``). has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. holomorphic: Optional, bool. Indicates whether ``fun`` is promised to be holomorphic. Default False. allow_int: Optional, bool. Whether to allow differentiating with respect to integer valued inputs. The gradient of an integer input will have a trivial vector-space dtype (float0). Default False. Returns: A function with the same arguments as ``fun``, that evaluates the Jacobian of ``fun`` using reverse-mode automatic differentiation. If ``has_aux`` is True then a pair of (jacobian, auxiliary_data) is returned. >>> import jax >>> import jax.numpy as jnp >>> >>> def f(x): ... return jnp.asarray( ... [x[0], 5*x[2], 4*x[1]**2 - 2*x[2], x[2] * jnp.sin(x[0])]) ... >>> print(jax.jacrev(f)(jnp.array([1., 2., 3.]))) [[ 1. 0. 0. ] [ 0. 0. 5. ] [ 0. 16. -2. ] [ 1.6209 0. 0.84147]] """ check_callable(fun) docstr = ("Jacobian of {fun} with respect to positional argument(s) " "{argnums}. Takes the same arguments as {fun} but returns the " "jacobian of the output with respect to the arguments at " "positions {argnums}.") @wraps(fun, docstr=docstr, argnums=argnums) def jacfun(*args, **kwargs): f = lu.wrap_init(fun, kwargs) f_partial, dyn_args = argnums_partial(f, argnums, args, require_static_args_hashable=False) tree_map(partial(_check_input_dtype_jacrev, holomorphic, allow_int), dyn_args) if not has_aux: y, pullback = _vjp(f_partial, *dyn_args) else: y, pullback, aux = _vjp(f_partial, *dyn_args, has_aux=True) tree_map(partial(_check_output_dtype_jacrev, holomorphic), y) jac = vmap(pullback)(_std_basis(y)) jac = jac[0] if isinstance(argnums, int) else jac example_args = dyn_args[0] if isinstance(argnums, int) else dyn_args jac_tree = tree_map(partial(_jacrev_unravel, y), example_args, jac) jac_tree = tree_transpose(tree_structure(example_args), tree_structure(y), jac_tree) if not has_aux: return jac_tree else: return jac_tree, aux return jacfun
jacobian = jacrev _check_input_dtype_jacrev = partial(_check_input_dtype_revderiv, "jacrev") _check_output_dtype_jacrev = partial(_check_output_dtype_revderiv, "jacrev")
[docs] def hessian(fun: Callable, argnums: int | Sequence[int] = 0, has_aux: bool = False, holomorphic: bool = False) -> Callable: """Hessian of ``fun`` as a dense array. Args: fun: Function whose Hessian is to be computed. Its arguments at positions specified by ``argnums`` should be arrays, scalars, or standard Python containers thereof. It should return arrays, scalars, or standard Python containers thereof. argnums: Optional, integer or sequence of integers. Specifies which positional argument(s) to differentiate with respect to (default ``0``). has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. holomorphic: Optional, bool. Indicates whether ``fun`` is promised to be holomorphic. Default False. Returns: A function with the same arguments as ``fun``, that evaluates the Hessian of ``fun``. >>> import jax >>> >>> g = lambda x: x[0]**3 - 2*x[0]*x[1] - x[1]**6 >>> print(jax.hessian(g)(jax.numpy.array([1., 2.]))) [[ 6. -2.] [ -2. -480.]] :py:func:`hessian` is a generalization of the usual definition of the Hessian that supports nested Python containers (i.e. pytrees) as inputs and outputs. The tree structure of ``jax.hessian(fun)(x)`` is given by forming a tree product of the structure of ``fun(x)`` with a tree product of two copies of the structure of ``x``. A tree product of two tree structures is formed by replacing each leaf of the first tree with a copy of the second. For example: >>> import jax.numpy as jnp >>> f = lambda dct: {"c": jnp.power(dct["a"], dct["b"])} >>> print(jax.hessian(f)({"a": jnp.arange(2.) + 1., "b": jnp.arange(2.) + 2.})) {'c': {'a': {'a': Array([[[ 2., 0.], [ 0., 0.]], [[ 0., 0.], [ 0., 12.]]], dtype=float32), 'b': Array([[[ 1. , 0. ], [ 0. , 0. ]], [[ 0. , 0. ], [ 0. , 12.317766]]], dtype=float32)}, 'b': {'a': Array([[[ 1. , 0. ], [ 0. , 0. ]], [[ 0. , 0. ], [ 0. , 12.317766]]], dtype=float32), 'b': Array([[[0. , 0. ], [0. , 0. ]], [[0. , 0. ], [0. , 3.843624]]], dtype=float32)}}} Thus each leaf in the tree structure of ``jax.hessian(fun)(x)`` corresponds to a leaf of ``fun(x)`` and a pair of leaves of ``x``. For each leaf in ``jax.hessian(fun)(x)``, if the corresponding array leaf of ``fun(x)`` has shape ``(out_1, out_2, ...)`` and the corresponding array leaves of ``x`` have shape ``(in_1_1, in_1_2, ...)`` and ``(in_2_1, in_2_2, ...)`` respectively, then the Hessian leaf has shape ``(out_1, out_2, ..., in_1_1, in_1_2, ..., in_2_1, in_2_2, ...)``. In other words, the Python tree structure represents the block structure of the Hessian, with blocks determined by the input and output pytrees. In particular, an array is produced (with no pytrees involved) when the function input ``x`` and output ``fun(x)`` are each a single array, as in the ``g`` example above. If ``fun(x)`` has shape ``(out1, out2, ...)`` and ``x`` has shape ``(in1, in2, ...)`` then ``jax.hessian(fun)(x)`` has shape ``(out1, out2, ..., in1, in2, ..., in1, in2, ...)``. To flatten pytrees into 1D vectors, consider using :py:func:`jax.flatten_util.flatten_pytree`. """ return jacfwd(jacrev(fun, argnums, has_aux=has_aux, holomorphic=holomorphic), argnums, has_aux=has_aux, holomorphic=holomorphic)
def _std_basis(pytree): import jax.numpy as jnp leaves, _ = tree_flatten(pytree) ndim = sum(map(np.size, leaves)) dtype = dtypes.result_type(*leaves) flat_basis = jnp.eye(ndim, dtype=dtype) return _unravel_array_into_pytree(pytree, 1, None, flat_basis) def _jacfwd_unravel(input_pytree, output_pytree_leaf, arr): return _unravel_array_into_pytree( input_pytree, -1, output_pytree_leaf, arr) def _jacrev_unravel(output_pytree, input_pytree_leaf, arr): return _unravel_array_into_pytree( output_pytree, 0, input_pytree_leaf, arr) def _possible_downcast(x, example): if (dtypes.issubdtype(x.dtype, np.complexfloating) and not dtypes.issubdtype(_dtype(example), np.complexfloating)): x = x.real dtype = None if example is None else _dtype(example) weak_type = None if example is None else dtypes.is_weakly_typed(example) return lax_internal._convert_element_type(x, dtype, weak_type) def _unravel_array_into_pytree(pytree, axis, example, arr): """Unravel an array into a PyTree with a given structure. Args: pytree: The pytree that provides the structure. axis: The parameter axis is either -1, 0, or 1. It controls the resulting shapes. example: If specified, cast the components to the matching dtype/weak_type, or else use the pytree leaf type if example is None. arr: The array to be unraveled. """ leaves, treedef = tree_flatten(pytree) axis = axis % arr.ndim shapes = [arr.shape[:axis] + np.shape(l) + arr.shape[axis+1:] for l in leaves] parts = _split(arr, np.cumsum(map(np.size, leaves[:-1])), axis) reshaped_parts = [ _possible_downcast(np.reshape(x, shape), leaf if example is None else example) for x, shape, leaf in zip(parts, shapes, leaves)] return tree_unflatten(treedef, reshaped_parts) def _split(x, indices, axis): if isinstance(x, np.ndarray): return np.split(x, indices, axis) else: return x._split(indices, axis)
[docs] def vmap(fun: F, in_axes: int | None | Sequence[Any] = 0, out_axes: Any = 0, axis_name: AxisName | None = None, axis_size: int | None = None, spmd_axis_name: AxisName | tuple[AxisName, ...] | None = None ) -> F: """Vectorizing map. Creates a function which maps ``fun`` over argument axes. Args: fun: Function to be mapped over additional axes. in_axes: An integer, None, or sequence of values specifying which input array axes to map over. If each positional argument to ``fun`` is an array, then ``in_axes`` can be an integer, a None, or a tuple of integers and Nones with length equal to the number of positional arguments to ``fun``. An integer or ``None`` indicates which array axis to map over for all arguments (with ``None`` indicating not to map any axis), and a tuple indicates which axis to map for each corresponding positional argument. Axis integers must be in the range ``[-ndim, ndim)`` for each array, where ``ndim`` is the number of dimensions (axes) of the corresponding input array. If the positional arguments to ``fun`` are container (pytree) types, ``in_axes`` must be a sequence with length equal to the number of positional arguments to ``fun``, and for each argument the corresponding element of ``in_axes`` can be a container with a matching pytree structure specifying the mapping of its container elements. In other words, ``in_axes`` must be a container tree prefix of the positional argument tuple passed to ``fun``. See this link for more detail: https://jax.readthedocs.io/en/latest/pytrees.html#applying-optional-parameters-to-pytrees Either ``axis_size`` must be provided explicitly, or at least one positional argument must have ``in_axes`` not None. The sizes of the mapped input axes for all mapped positional arguments must all be equal. Arguments passed as keywords are always mapped over their leading axis (i.e. axis index 0). See below for examples. out_axes: An integer, None, or (nested) standard Python container (tuple/list/dict) thereof indicating where the mapped axis should appear in the output. All outputs with a mapped axis must have a non-None ``out_axes`` specification. Axis integers must be in the range ``[-ndim, ndim)`` for each output array, where ``ndim`` is the number of dimensions (axes) of the array returned by the :func:`vmap`-ed function, which is one more than the number of dimensions (axes) of the corresponding array returned by ``fun``. axis_name: Optional, a hashable Python object used to identify the mapped axis so that parallel collectives can be applied. axis_size: Optional, an integer indicating the size of the axis to be mapped. If not provided, the mapped axis size is inferred from arguments. Returns: Batched/vectorized version of ``fun`` with arguments that correspond to those of ``fun``, but with extra array axes at positions indicated by ``in_axes``, and a return value that corresponds to that of ``fun``, but with extra array axes at positions indicated by ``out_axes``. For example, we can implement a matrix-matrix product using a vector dot product: >>> import jax.numpy as jnp >>> >>> vv = lambda x, y: jnp.vdot(x, y) # ([a], [a]) -> [] >>> mv = vmap(vv, (0, None), 0) # ([b,a], [a]) -> [b] (b is the mapped axis) >>> mm = vmap(mv, (None, 1), 1) # ([b,a], [a,c]) -> [b,c] (c is the mapped axis) Here we use ``[a,b]`` to indicate an array with shape (a,b). Here are some variants: >>> mv1 = vmap(vv, (0, 0), 0) # ([b,a], [b,a]) -> [b] (b is the mapped axis) >>> mv2 = vmap(vv, (0, 1), 0) # ([b,a], [a,b]) -> [b] (b is the mapped axis) >>> mm2 = vmap(mv2, (1, 1), 0) # ([b,c,a], [a,c,b]) -> [c,b] (c is the mapped axis) Here's an example of using container types in ``in_axes`` to specify which axes of the container elements to map over: >>> A, B, C, D = 2, 3, 4, 5 >>> x = jnp.ones((A, B)) >>> y = jnp.ones((B, C)) >>> z = jnp.ones((C, D)) >>> def foo(tree_arg): ... x, (y, z) = tree_arg ... return jnp.dot(x, jnp.dot(y, z)) >>> tree = (x, (y, z)) >>> print(foo(tree)) [[12. 12. 12. 12. 12.] [12. 12. 12. 12. 12.]] >>> from jax import vmap >>> K = 6 # batch size >>> x = jnp.ones((K, A, B)) # batch axis in different locations >>> y = jnp.ones((B, K, C)) >>> z = jnp.ones((C, D, K)) >>> tree = (x, (y, z)) >>> vfoo = vmap(foo, in_axes=((0, (1, 2)),)) >>> print(vfoo(tree).shape) (6, 2, 5) Here's another example using container types in ``in_axes``, this time a dictionary, to specify the elements of the container to map over: >>> dct = {'a': 0., 'b': jnp.arange(5.)} >>> x = 1. >>> def foo(dct, x): ... return dct['a'] + dct['b'] + x >>> out = vmap(foo, in_axes=({'a': None, 'b': 0}, None))(dct, x) >>> print(out) [1. 2. 3. 4. 5.] The results of a vectorized function can be mapped or unmapped. For example, the function below returns a pair with the first element mapped and the second unmapped. Only for unmapped results we can specify ``out_axes`` to be ``None`` (to keep it unmapped). >>> print(vmap(lambda x, y: (x + y, y * 2.), in_axes=(0, None), out_axes=(0, None))(jnp.arange(2.), 4.)) (Array([4., 5.], dtype=float32), 8.0) If the ``out_axes`` is specified for an unmapped result, the result is broadcast across the mapped axis: >>> print(vmap(lambda x, y: (x + y, y * 2.), in_axes=(0, None), out_axes=0)(jnp.arange(2.), 4.)) (Array([4., 5.], dtype=float32), Array([8., 8.], dtype=float32, weak_type=True)) If the ``out_axes`` is specified for a mapped result, the result is transposed accordingly. Finally, here's an example using ``axis_name`` together with collectives: >>> xs = jnp.arange(3. * 4.).reshape(3, 4) >>> print(vmap(lambda x: lax.psum(x, 'i'), axis_name='i')(xs)) [[12. 15. 18. 21.] [12. 15. 18. 21.] [12. 15. 18. 21.]] See the :py:func:`jax.pmap` docstring for more examples involving collectives. """ check_callable(fun) docstr = ("Vectorized version of {fun}. Takes similar arguments as {fun} " "but with additional array axes over which {fun} is mapped.") if fun.__doc__: docstr += "\n\nOriginal documentation:\n\n" docstr += fun.__doc__ axis_name = core.no_axis_name if axis_name is None else axis_name if spmd_axis_name is not None and type(spmd_axis_name) is not tuple: spmd_axis_name = (spmd_axis_name,) if isinstance(in_axes, list): # To be a tree prefix of the positional args tuple, in_axes can never be a # list: if in_axes is not a leaf, it must be a tuple of trees. However, # in cases like these users expect tuples and lists to be treated # essentially interchangeably, so we canonicalize lists to tuples here # rather than raising an error. https://github.com/google/jax/issues/2367 in_axes = tuple(in_axes) if not (in_axes is None or type(in_axes) in {int, tuple, *batching.spec_types}): raise TypeError("vmap in_axes must be an int, None, or a tuple of entries corresponding " f"to the positional arguments passed to the function, but got {in_axes}.") if not all(type(l) in {int, *batching.spec_types} for l in tree_leaves(in_axes)): raise TypeError("vmap in_axes must be an int, None, or (nested) container " f"with those types as leaves, but got {in_axes}.") if not all(type(l) in {int, *batching.spec_types} for l in tree_leaves(out_axes)): raise TypeError("vmap out_axes must be an int, None, or (nested) container " f"with those types as leaves, but got {out_axes}.") @wraps(fun, docstr=docstr) @api_boundary def vmap_f(*args, **kwargs): if isinstance(in_axes, tuple) and len(in_axes) != len(args): raise ValueError("vmap in_axes must be an int, None, or a tuple of entries corresponding " "to the positional arguments passed to the function, " f"but got {len(in_axes)=}, {len(args)=}") args_flat, in_tree = tree_flatten((args, kwargs), is_leaf=batching.is_vmappable) f = lu.wrap_init(fun) flat_fun, out_tree = batching.flatten_fun_for_vmap(f, in_tree) in_axes_flat = flatten_axes("vmap in_axes", in_tree, (in_axes, 0), kws=True) axis_size_ = (axis_size if axis_size is not None else _mapped_axis_size(fun, in_tree, args_flat, in_axes_flat, "vmap")) out_flat = batching.batch( flat_fun, axis_name, axis_size_, in_axes_flat, lambda: flatten_axes("vmap out_axes", out_tree(), out_axes), spmd_axis_name=spmd_axis_name ).call_wrapped(*args_flat) return tree_unflatten(out_tree(), out_flat) return cast(F, vmap_f)
def _mapped_axis_size(fn, tree, vals, dims, name): if not vals: args, kwargs = tree_unflatten(tree, vals) raise ValueError( f"{name} wrapped function must be passed at least one argument " f"containing an array, got empty *args={args} and **kwargs={kwargs}" ) def _get_axis_size(name: str, shape: tuple[core.AxisSize, ...], axis: int ) -> core.AxisSize: try: return shape[axis] except (IndexError, TypeError) as e: min_rank = axis + 1 if axis >= 0 else -axis # TODO(mattjj): better error message here raise ValueError( f"{name} was requested to map its argument along axis {axis}, " f"which implies that its rank should be at least {min_rank}, " f"but is only {len(shape)} (its shape is {shape})") from e sizes = core.dedup_referents(_get_axis_size(name, np.shape(x), d) for x, d in zip(vals, dims) if d is not None) if len(sizes) == 1: sz, = sizes return sz if not sizes: msg = f"{name} must have at least one non-None value in in_axes" raise ValueError(msg) def _get_argument_type(x): try: return shaped_abstractify(x).str_short() except TypeError: #Catch all for user specified objects that can't be interpreted as a data type return "unknown" msg = [f"{name} got inconsistent sizes for array axes to be mapped:\n"] args, kwargs = tree_unflatten(tree, vals) try: ba = inspect.signature(fn).bind(*args, **kwargs) except (TypeError, ValueError): ba = None if ba is None: args_paths = [f'args{keystr(p)} ' f'of type {_get_argument_type(x)}' for p, x in generate_key_paths(args)] kwargs_paths = [f'kwargs{keystr(p)} ' f'of type {_get_argument_type(x)}' for p, x in generate_key_paths(kwargs)] key_paths = [*args_paths, *kwargs_paths] else: key_paths = [f'argument {name}{keystr(p)} ' f'of type {_get_argument_type(x)}' for name, arg in ba.arguments.items() for p, x in generate_key_paths(arg)] all_sizes = [_get_axis_size(name, np.shape(x), d) if d is not None else None for x, d in zip(vals, dims)] size_counts = collections.Counter(s for s in all_sizes if s is not None) (sz, ct), *other_counts = counts = size_counts.most_common() def _all_sizes_index(sz): for i, isz in enumerate(all_sizes): if core.definitely_equal(isz, sz): return i assert False, (sz, all_sizes) ex, *examples = (key_paths[_all_sizes_index(sz)] for sz, _ in counts) ax, *axs = (dims[_all_sizes_index(sz)] for sz, _ in counts) if ct == 1: msg.append(f" * one axis had size {sz}: axis {ax} of {ex};\n") else: msg.append(f" * most axes ({ct} of them) had size {sz}, e.g. axis {ax} of {ex};\n") for ex, ax, (sz, ct) in zip(examples, axs, other_counts): if ct == 1: msg.append(f" * one axis had size {sz}: axis {ax} of {ex};\n") else: msg.append(f" * some axes ({ct} of them) had size {sz}, e.g. axis {ax} of {ex};\n") raise ValueError(''.join(msg)[:-2]) # remove last semicolon and newline
[docs] def pmap( fun: Callable, axis_name: AxisName | None = None, *, in_axes=0, out_axes=0, static_broadcasted_argnums: int | Iterable[int] = (), devices: Sequence[xc.Device] | None = None, # noqa: F811 backend: str | None = None, axis_size: int | None = None, donate_argnums: int | Iterable[int] = (), global_arg_shapes: tuple[tuple[int, ...], ...] | None = None, ) -> Any: """Parallel map with support for collective operations. The purpose of :py:func:`pmap` is to express single-program multiple-data (SPMD) programs. Applying :py:func:`pmap` to a function will compile the function with XLA (similarly to :py:func:`jit`), then execute it in parallel on XLA devices, such as multiple GPUs or multiple TPU cores. Semantically it is comparable to :py:func:`vmap` because both transformations map a function over array axes, but where :py:func:`vmap` vectorizes functions by pushing the mapped axis down into primitive operations, :py:func:`pmap` instead replicates the function and executes each replica on its own XLA device in parallel. The mapped axis size must be less than or equal to the number of local XLA devices available, as returned by :py:func:`jax.local_device_count()` (unless ``devices`` is specified, see below). For nested :py:func:`pmap` calls, the product of the mapped axis sizes must be less than or equal to the number of XLA devices. .. note:: :py:func:`pmap` compiles ``fun``, so while it can be combined with :py:func:`jit`, it's usually unnecessary. :py:func:`pmap` requires that all of the participating devices are identical. For example, it is not possible to use :py:func:`pmap` to parallelize a computation across two different models of GPU. It is currently an error for the same device to participate twice in the same `pmap`. **Multi-process platforms:** On multi-process platforms such as TPU pods, :py:func:`pmap` is designed to be used in SPMD Python programs, where every process is running the same Python code such that all processes run the same pmapped function in the same order. Each process should still call the pmapped function with mapped axis size equal to the number of *local* devices (unless ``devices`` is specified, see below), and an array of the same leading axis size will be returned as usual. However, any collective operations in ``fun`` will be computed over *all* participating devices, including those on other processes, via device-to-device communication. Conceptually, this can be thought of as running a pmap over a single array sharded across processes, where each process "sees" only its local shard of the input and output. The SPMD model requires that the same multi-process pmaps must be run in the same order on all devices, but they can be interspersed with arbitrary operations running in a single process. Args: fun: Function to be mapped over argument axes. Its arguments and return value should be arrays, scalars, or (nested) standard Python containers (tuple/list/dict) thereof. Positional arguments indicated by ``static_broadcasted_argnums`` can be anything at all, provided they are hashable and have an equality operation defined. axis_name: Optional, a hashable Python object used to identify the mapped axis so that parallel collectives can be applied. in_axes: A non-negative integer, None, or nested Python container thereof that specifies which axes of positional arguments to map over. Arguments passed as keywords are always mapped over their leading axis (i.e. axis index 0). See :py:func:`vmap` for details. out_axes: A non-negative integer, None, or nested Python container thereof indicating where the mapped axis should appear in the output. All outputs with a mapped axis must have a non-None ``out_axes`` specification (see :py:func:`vmap`). static_broadcasted_argnums: An int or collection of ints specifying which positional arguments to treat as static (compile-time constant). Operations that only depend on static arguments will be constant-folded. Calling the pmapped function with different values for these constants will trigger recompilation. If the pmapped function is called with fewer positional arguments than indicated by ``static_broadcasted_argnums`` then an error is raised. Each of the static arguments will be broadcasted to all devices. Arguments that are not arrays or containers thereof must be marked as static. Defaults to (). Static arguments must be hashable, meaning both ``__hash__`` and ``__eq__`` are implemented, and should be immutable. devices: This is an experimental feature and the API is likely to change. Optional, a sequence of Devices to map over. (Available devices can be retrieved via jax.devices()). Must be given identically for each process in multi-process settings (and will therefore include devices across processes). If specified, the size of the mapped axis must be equal to the number of devices in the sequence local to the given process. Nested :py:func:`pmap` s with ``devices`` specified in either the inner or outer :py:func:`pmap` are not yet supported. backend: This is an experimental feature and the API is likely to change. Optional, a string representing the XLA backend. 'cpu', 'gpu', or 'tpu'. axis_size: Optional; the size of the mapped axis. donate_argnums: Specify which positional argument buffers are "donated" to the computation. It is safe to donate argument buffers if you no longer need them once the computation has finished. In some cases XLA can make use of donated buffers to reduce the amount of memory needed to perform a computation, for example recycling one of your input buffers to store a result. You should not reuse buffers that you donate to a computation, JAX will raise an error if you try to. Note that donate_argnums only work for positional arguments, and keyword arguments will not be donated. For more details on buffer donation see the `FAQ <https://jax.readthedocs.io/en/latest/faq.html#buffer-donation>`_. Returns: A parallelized version of ``fun`` with arguments that correspond to those of ``fun`` but with extra array axes at positions indicated by ``in_axes`` and with output that has an additional leading array axis (with the same size). For example, assuming 8 XLA devices are available, :py:func:`pmap` can be used as a map along a leading array axis: >>> import jax.numpy as jnp >>> >>> out = pmap(lambda x: x ** 2)(jnp.arange(8)) # doctest: +SKIP >>> print(out) # doctest: +SKIP [0, 1, 4, 9, 16, 25, 36, 49] When the leading dimension is smaller than the number of available devices JAX will simply run on a subset of devices: >>> x = jnp.arange(3 * 2 * 2.).reshape((3, 2, 2)) >>> y = jnp.arange(3 * 2 * 2.).reshape((3, 2, 2)) ** 2 >>> out = pmap(jnp.dot)(x, y) # doctest: +SKIP >>> print(out) # doctest: +SKIP [[[ 4. 9.] [ 12. 29.]] [[ 244. 345.] [ 348. 493.]] [[ 1412. 1737.] [ 1740. 2141.]]] If your leading dimension is larger than the number of available devices you will get an error: >>> pmap(lambda x: x ** 2)(jnp.arange(9)) # doctest: +SKIP ValueError: ... requires 9 replicas, but only 8 XLA devices are available As with :py:func:`vmap`, using ``None`` in ``in_axes`` indicates that an argument doesn't have an extra axis and should be broadcasted, rather than mapped, across the replicas: >>> x, y = jnp.arange(2.), 4. >>> out = pmap(lambda x, y: (x + y, y * 2.), in_axes=(0, None))(x, y) # doctest: +SKIP >>> print(out) # doctest: +SKIP ([4., 5.], [8., 8.]) Note that :py:func:`pmap` always returns values mapped over their leading axis, equivalent to using ``out_axes=0`` in :py:func:`vmap`. In addition to expressing pure maps, :py:func:`pmap` can also be used to express parallel single-program multiple-data (SPMD) programs that communicate via collective operations. For example: >>> f = lambda x: x / jax.lax.psum(x, axis_name='i') >>> out = pmap(f, axis_name='i')(jnp.arange(4.)) # doctest: +SKIP >>> print(out) # doctest: +SKIP [ 0. 0.16666667 0.33333334 0.5 ] >>> print(out.sum()) # doctest: +SKIP 1.0 In this example, ``axis_name`` is a string, but it can be any Python object with ``__hash__`` and ``__eq__`` defined. The argument ``axis_name`` to :py:func:`pmap` names the mapped axis so that collective operations, like :func:`jax.lax.psum`, can refer to it. Axis names are important particularly in the case of nested :py:func:`pmap` functions, where collective operations can operate over distinct axes: >>> from functools import partial >>> import jax >>> >>> @partial(pmap, axis_name='rows') ... @partial(pmap, axis_name='cols') ... def normalize(x): ... row_normed = x / jax.lax.psum(x, 'rows') ... col_normed = x / jax.lax.psum(x, 'cols') ... doubly_normed = x / jax.lax.psum(x, ('rows', 'cols')) ... return row_normed, col_normed, doubly_normed >>> >>> x = jnp.arange(8.).reshape((4, 2)) >>> row_normed, col_normed, doubly_normed = normalize(x) # doctest: +SKIP >>> print(row_normed.sum(0)) # doctest: +SKIP [ 1. 1.] >>> print(col_normed.sum(1)) # doctest: +SKIP [ 1. 1. 1. 1.] >>> print(doubly_normed.sum((0, 1))) # doctest: +SKIP 1.0 On multi-process platforms, collective operations operate over all devices, including those on other processes. For example, assuming the following code runs on two processes with 4 XLA devices each: >>> f = lambda x: x + jax.lax.psum(x, axis_name='i') >>> data = jnp.arange(4) if jax.process_index() == 0 else jnp.arange(4, 8) >>> out = pmap(f, axis_name='i')(data) # doctest: +SKIP >>> print(out) # doctest: +SKIP [28 29 30 31] # on process 0 [32 33 34 35] # on process 1 Each process passes in a different length-4 array, corresponding to its 4 local devices, and the psum operates over all 8 values. Conceptually, the two length-4 arrays can be thought of as a sharded length-8 array (in this example equivalent to jnp.arange(8)) that is mapped over, with the length-8 mapped axis given name 'i'. The pmap call on each process then returns the corresponding length-4 output shard. The ``devices`` argument can be used to specify exactly which devices are used to run the parallel computation. For example, again assuming a single process with 8 devices, the following code defines two parallel computations, one which runs on the first six devices and one on the remaining two: >>> from functools import partial >>> @partial(pmap, axis_name='i', devices=jax.devices()[:6]) ... def f1(x): ... return x / jax.lax.psum(x, axis_name='i') >>> >>> @partial(pmap, axis_name='i', devices=jax.devices()[-2:]) ... def f2(x): ... return jax.lax.psum(x ** 2, axis_name='i') >>> >>> print(f1(jnp.arange(6.))) # doctest: +SKIP [0. 0.06666667 0.13333333 0.2 0.26666667 0.33333333] >>> print(f2(jnp.array([2., 3.]))) # doctest: +SKIP [ 13. 13.] """ if global_arg_shapes is not None: raise ValueError( "global_arg_shapes only worked with sharded_jit which has long been" " removed from JAX. Please migrate to pjit and remove global_arg_shapes" " from pmap.") # TODO(yashkatariya): Move this out after shard_map is out of experimental and # in _src if config.pmap_shmap_merge.value: from jax.experimental.shard_map import pmap return pmap(fun, axis_name, in_axes=in_axes, out_axes=out_axes, static_broadcasted_argnums=static_broadcasted_argnums, devices=devices, backend=backend, axis_size=axis_size, donate_argnums=donate_argnums) return _cpp_pmap( fun, axis_name, in_axes=in_axes, out_axes=out_axes, static_broadcasted_argnums=static_broadcasted_argnums, devices=devices, backend=backend, axis_size=axis_size, donate_argnums=donate_argnums)
class PmapCallInfo(NamedTuple): flat_fun: lu.WrappedFun in_tree: PyTreeDef out_tree: Callable[[], PyTreeDef] flat_args: Sequence[Any] donated_invars: Sequence[bool] in_axes_flat: Sequence[int | None] local_axis_size: int out_axes_thunk: Callable devices: Sequence[xc.Device] | None global_axis_size: int is_explicit_global_axis_size: bool def _get_global_axis_size(local_axis_size: int, in_devices, backend_name: str, global_axis_size: int | None): """Determine global_axis_size for multi-host pmap.""" # TODO(mattjj,skyewm): revive this check (inner_pmap always False now) # if xb.process_count() > 1 and global_axis_size is None and inner_pmap: # raise ValueError("'axis_size' must be specified for nested multi-host pmaps") if (xb.process_count() == 1 and global_axis_size is not None and global_axis_size != local_axis_size): raise ValueError( f"Specified axis_size {global_axis_size} doesn't match received " f"axis_size {local_axis_size}.") if in_devices is not None and backend_name is None: backend = xb.get_device_backend(in_devices[0]) else: backend = xb.get_backend(backend_name) if global_axis_size is None: if xb.process_count(backend) == 1: global_axis_size = local_axis_size elif in_devices: global_axis_size = len(in_devices) else: global_axis_size = local_axis_size * xb.process_count(backend) assert all( len(xb.local_devices(pi, backend)) == xb.local_device_count(backend) for pi in range(xb.process_count(backend))) return global_axis_size def _prepare_pmap(fun, in_axes, out_axes, static_broadcasted_tuple, donate_tuple, in_devices, backend_name, axis_size, args, kwargs): if in_devices is not None and len(in_devices) == 0: raise ValueError("'devices' argument to pmap must be non-empty, or None.") src = fun_sourceinfo(fun) signature = api_util.fun_signature(fun) dbg = debug_info('pmap', src, signature, args, kwargs, static_broadcasted_tuple, ()) f = lu.wrap_init(fun) if static_broadcasted_tuple: if max(static_broadcasted_tuple) >= len(args): raise ValueError( f"pmapped function has static_broadcasted_argnums={static_broadcasted_tuple}" f" but was called with only {len(args)} positional " f"argument{'s' if len(args) > 1 else ''}. " "All static broadcasted arguments must be passed positionally.") dyn_argnums = [i for i in range(len(args)) if i not in static_broadcasted_tuple] f, dyn_args = argnums_partial(f, dyn_argnums, args) if isinstance(in_axes, tuple): dyn_in_axes = tuple(in_axes[i] for i in dyn_argnums) else: dyn_in_axes = in_axes else: dyn_args, dyn_in_axes = args, in_axes args, in_tree = tree_flatten((dyn_args, kwargs)) if donate_tuple and not config.debug_nans.value: donated_invars = donation_vector(donate_tuple, (), dyn_args, kwargs) else: donated_invars = (False,) * len(args) try: in_axes_flat = tuple(broadcast_prefix((dyn_in_axes, 0), (dyn_args, kwargs), is_leaf=lambda x: x is None)) except ValueError: e, *_ = prefix_errors((dyn_in_axes, 0), (dyn_args, kwargs)) ex = e('pmap in_axes') msg, = ex.args msg += ("\n\nThe 'full pytree' here is the tuple of arguments passed " "positionally to the pmapped function, and the value of `in_axes` " "must be a tree prefix of that tuple. But it was not a prefix.") if kwargs: msg += ("\n\nWhen some arguments are passed by keyword to the pmapped " "function, they are not included in the comparison to `in_axes`. " "Instead, each argument passed by keyword is mapped over its " "leading axis. See the description of `in_axes` in the `pmap` " "docstring: " "https://jax.readthedocs.io/en/latest/_autosummary/jax.pmap.html#jax.pmap") msg += ("\n\nCheck that the value of the `in_axes` argument to `pmap` " "is a tree prefix of the tuple of arguments passed positionally to " "the pmapped function.") raise ValueError(msg) from None local_axis_size = _mapped_axis_size(fun, in_tree, args, in_axes_flat, "pmap") f, res_paths = result_paths(f) f, out_axes_thunk = flat_out_axes(f, out_axes) flat_fun, out_tree = flatten_fun(f, in_tree) flat_fun = debug_info_final(flat_fun, dbg, res_paths) is_explicit_global_axis_size = axis_size is not None global_axis_size = _get_global_axis_size(local_axis_size, in_devices, backend_name, axis_size) return PmapCallInfo(flat_fun=flat_fun, in_tree=in_tree, out_tree=out_tree, flat_args=args, donated_invars=donated_invars, in_axes_flat=in_axes_flat, local_axis_size=local_axis_size, out_axes_thunk=out_axes_thunk, devices=None if in_devices is None else tuple(in_devices), global_axis_size=global_axis_size, is_explicit_global_axis_size=is_explicit_global_axis_size) def _shared_code_pmap(fun, axis_name, static_broadcasted_argnums, donate_argnums, in_axes, out_axes): # axis_size is an optional integer representing the global axis size. The # aggregate size (across all processes) size of the mapped axis must match the # given value. check_callable(fun) axis_name = core._TempAxisName(fun) if axis_name is None else axis_name static_broadcasted_tuple = _ensure_index_tuple(static_broadcasted_argnums) donate_tuple = rebase_donate_argnums( _ensure_index_tuple(donate_argnums), static_broadcasted_tuple) if not all(type(l) is int for l in tree_leaves(in_axes)): raise TypeError("pmap in_axes must be an int, None, or (nested) container " f"with those types as leaves, but got {in_axes}.") if not all(type(l) is int for l in tree_leaves(out_axes)): raise TypeError("pmap out_axes must be an int, None, or (nested) container " f"with those types as leaves, but got {out_axes}.") return axis_name, static_broadcasted_tuple, donate_tuple class _PmapFastpathData(NamedTuple): version: int # For forward and backward compatibility xla_executable: xc.LoadedExecutable in_handler: Any out_handler: Any out_pytree_def: Any # Data needed to handle the inputs. input_devices: Sequence[xc.Device] input_indices: Sequence[sharding_specs.Index] input_array_shardings: Sequence[Any] # Data needed to build the Array from C++. out_avals: Sequence[Any] out_array_shardings: Sequence[Any] out_committed: Sequence[Any] def _cpp_pmap( fun: Callable, axis_name: AxisName | None = None, *, in_axes=0, out_axes=0, static_broadcasted_argnums: int | Iterable[int] = (), devices: Sequence[xc.Device] | None = None, # noqa: F811 backend: str | None = None, axis_size: int | None = None, donate_argnums: int | Iterable[int] = (), ) -> Any: axis_name, static_broadcasted_tuple, donate_tuple = _shared_code_pmap( fun, axis_name, static_broadcasted_argnums, donate_argnums, in_axes, out_axes) del static_broadcasted_argnums, donate_argnums @api_boundary def cache_miss(*args, **kwargs): p = _prepare_pmap(fun, in_axes, out_axes, static_broadcasted_tuple, donate_tuple, devices, backend, axis_size, args, kwargs) for arg in p.flat_args: dispatch.check_arg(arg) params = dict( backend=backend, axis_name=axis_name, axis_size=p.local_axis_size, global_axis_size=p.global_axis_size, devices=p.devices, in_axes=p.in_axes_flat, out_axes_thunk=p.out_axes_thunk, name=p.flat_fun.__name__, donated_invars=p.donated_invars, is_explicit_global_axis_size=p.is_explicit_global_axis_size, ) map_bind_continuation, top_trace, fun_, tracers, params = ( core.map_bind_with_continuation(pxla.xla_pmap_p, p.flat_fun, *p.flat_args, **params)) execute: Callable | None = None if isinstance(top_trace, core.EvalTrace): execute = pxla.xla_pmap_impl_lazy(fun_, *tracers, **params) out = map_bind_continuation(execute(*tracers)) else: out = map_bind_continuation( pxla.xla_pmap_p.process(top_trace, fun_, tracers, params)) out_tree, out_flat = p.out_tree, out out_pytree_def = out_tree() out = tree_unflatten(out_pytree_def, out_flat) ### Decide whether we can support the C++ fast path use_fastpath = False if execute is not None and isinstance(execute, pxla.ExecuteReplicated): execute_replicated = typing.cast(pxla.ExecuteReplicated, execute) use_fastpath = ( # TODO(sharadmv): Enable effects in replicated computation not execute_replicated.has_unordered_effects and not execute_replicated.has_host_callbacks and # No tracers in the outputs. all(isinstance(x, xc.ArrayImpl) for x in out_flat)) ### If we can use the fastpath, we return required info to the caller. if use_fastpath: execute_replicated = typing.cast(pxla.ExecuteReplicated, execute) out_handler = execute_replicated.out_handler in_handler = execute_replicated.in_handler out_array_shardings = [out.sharding for out in out_flat] out_committed = [out._committed for out in out_flat] fastpath_data = _PmapFastpathData( version=1, xla_executable=execute_replicated.xla_executable, in_handler=in_handler, out_handler=out_handler, out_pytree_def=out_pytree_def, input_devices=in_handler.local_devices, input_indices=in_handler.input_indices, input_array_shardings=in_handler.in_shardings, out_avals=out_handler.out_avals, out_array_shardings=out_array_shardings, out_committed=out_committed, ) else: fastpath_data = None return out, fastpath_data cpp_mapped_f = pmap_lib.pmap( fun, cache_miss, static_broadcasted_tuple, pxla.shard_arg if xla_extension_version >= 229 else pxla.temp_shard_arg, # type: ignore pytree_registry=tree_util.default_registry) _pmap_cache_clears.add(cpp_mapped_f) pmap_f = wraps(fun)(cpp_mapped_f) pmap_f.lower = _pmap_lower( fun, axis_name, in_axes, out_axes, static_broadcasted_tuple, devices, backend, axis_size, donate_tuple) return pmap_f _pmap_cache_clears = weakref.WeakSet() # type: ignore def _pmap_lower(fun, axis_name, in_axes, out_axes, static_broadcasted_tuple, devices, backend, axis_size, donate_tuple): # noqa: F811 """Make a ``lower`` method for pmapped functions.""" # If the function we returned from ``pmap`` were a class instance, # this might naturally be a method, with ``fun`` as a ``self`` and # all the other arguments stored as attributes. @api_boundary def lower(*args, **kwargs) -> stages.Lowered: """Lower a parallel-mapped form of this function for the given arguments. A parallel-mapped and lowered function is staged out of Python and translated to a compiler's input language, possibly in a backend-dependent manner. It is ready for compilation but is not yet compiled. It represents a function intended for SPMD execution on multiple devices. Returns: A ``Lowered`` instance representing the post-map lowering. """ lowering_parameters = kwargs.pop( '_experimental_lowering_parameters', mlir.LoweringParameters()) p = _prepare_pmap( fun, in_axes, out_axes, static_broadcasted_tuple, donate_tuple, devices, backend, axis_size, args, kwargs) abstract_args = list(map(shaped_abstractify, p.flat_args)) computation = pxla.lower_parallel_callable( p.flat_fun, backend, axis_name, axis_size=p.local_axis_size, global_axis_size=p.global_axis_size, devices=p.devices, name=p.flat_fun.__name__, in_axes=p.in_axes_flat, out_axes_thunk=p.out_axes_thunk, donated_invars=p.donated_invars, is_explicit_global_axis_size=p.is_explicit_global_axis_size, avals=abstract_args, lowering_parameters=lowering_parameters) return stages.Lowered.from_flat_info( computation, p.in_tree, abstract_args, donate_tuple, p.out_tree()) return lower
[docs] def jvp( fun: Callable, primals, tangents, has_aux: bool = False ) -> tuple[Any, ...]: """Computes a (forward-mode) Jacobian-vector product of ``fun``. Args: fun: Function to be differentiated. Its arguments should be arrays, scalars, or standard Python containers of arrays or scalars. It should return an array, scalar, or standard Python container of arrays or scalars. primals: The primal values at which the Jacobian of ``fun`` should be evaluated. Should be either a tuple or a list of arguments, and its length should be equal to the number of positional parameters of ``fun``. tangents: The tangent vector for which the Jacobian-vector product should be evaluated. Should be either a tuple or a list of tangents, with the same tree structure and array shapes as ``primals``. has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. Returns: If ``has_aux`` is ``False``, returns a ``(primals_out, tangents_out)`` pair, where ``primals_out`` is ``fun(*primals)``, and ``tangents_out`` is the Jacobian-vector product of ``function`` evaluated at ``primals`` with ``tangents``. The ``tangents_out`` value has the same Python tree structure and shapes as ``primals_out``. If ``has_aux`` is ``True``, returns a ``(primals_out, tangents_out, aux)`` tuple where ``aux`` is the auxiliary data returned by ``fun``. For example: >>> import jax >>> >>> primals, tangents = jax.jvp(jax.numpy.sin, (0.1,), (0.2,)) >>> print(primals) 0.09983342 >>> print(tangents) 0.19900084 """ check_callable(fun) return _jvp(lu.wrap_init(fun), primals, tangents, has_aux=has_aux)
def _jvp(fun: lu.WrappedFun, primals, tangents, has_aux=False): """Variant of jvp() that takes an lu.WrappedFun.""" if (not isinstance(primals, (tuple, list)) or not isinstance(tangents, (tuple, list))): raise TypeError("primal and tangent arguments to jax.jvp must be tuples or lists; " f"found {type(primals).__name__} and {type(tangents).__name__}.") ps_flat, tree_def = tree_flatten(primals) ts_flat, tree_def_2 = tree_flatten(tangents) if tree_def != tree_def_2: raise TypeError("primal and tangent arguments to jax.jvp must have the same tree " f"structure; primals have tree structure {tree_def} whereas tangents have " f"tree structure {tree_def_2}.") for p, t in safe_zip(ps_flat, ts_flat): if core.primal_dtype_to_tangent_dtype(_dtype(p)) != _dtype(t): raise TypeError("primal and tangent arguments to jax.jvp do not match; " "dtypes must be equal, or in case of int/bool primal dtype " "the tangent dtype must be float0." f"Got primal dtype {_dtype(p)} and so expected tangent dtype " f"{core.primal_dtype_to_tangent_dtype(_dtype(p))}, but got " f"tangent dtype {_dtype(t)} instead.") if np.shape(p) != np.shape(t): raise ValueError("jvp called with different primal and tangent shapes;" f"Got primal shape {np.shape(p)} and tangent shape as {np.shape(t)}") if not has_aux: flat_fun, out_tree = flatten_fun_nokwargs(fun, tree_def) out_primals, out_tangents = ad.jvp(flat_fun).call_wrapped(ps_flat, ts_flat) out_tree = out_tree() return (tree_unflatten(out_tree, out_primals), tree_unflatten(out_tree, out_tangents)) else: flat_fun, out_aux_trees = flatten_fun_nokwargs2(fun, tree_def) jvp_fun, aux = ad.jvp(flat_fun, has_aux=True) out_primals, out_tangents = jvp_fun.call_wrapped(ps_flat, ts_flat) out_tree, aux_tree = out_aux_trees() return (tree_unflatten(out_tree, out_primals), tree_unflatten(out_tree, out_tangents), tree_unflatten(aux_tree, aux())) @overload def linearize(fun: Callable, *primals, has_aux: Literal[False] = False ) -> tuple[Any, Callable]: ... @overload def linearize(fun: Callable, *primals, has_aux: Literal[True] ) -> tuple[Any, Callable, Any]: ...
[docs] def linearize(fun: Callable, *primals, has_aux: bool = False ) -> tuple[Any, Callable] | tuple[Any, Callable, Any]: """Produces a linear approximation to ``fun`` using :py:func:`jvp` and partial eval. Args: fun: Function to be differentiated. Its arguments should be arrays, scalars, or standard Python containers of arrays or scalars. It should return an array, scalar, or standard python container of arrays or scalars. primals: The primal values at which the Jacobian of ``fun`` should be evaluated. Should be a tuple of arrays, scalar, or standard Python container thereof. The length of the tuple is equal to the number of positional parameters of ``fun``. has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be linearized, and the second is auxiliary data. Default False. Returns: If ``has_aux`` is ``False``, returns a pair where the first element is the value of ``f(*primals)`` and the second element is a function that evaluates the (forward-mode) Jacobian-vector product of ``fun`` evaluated at ``primals`` without re-doing the linearization work. If ``has_aux`` is ``True``, returns a ``(primals_out, lin_fn, aux)`` tuple where ``aux`` is the auxiliary data returned by ``fun``. In terms of values computed, :py:func:`linearize` behaves much like a curried :py:func:`jvp`, where these two code blocks compute the same values:: y, out_tangent = jax.jvp(f, (x,), (in_tangent,)) y, f_jvp = jax.linearize(f, x) out_tangent = f_jvp(in_tangent) However, the difference is that :py:func:`linearize` uses partial evaluation so that the function ``f`` is not re-linearized on calls to ``f_jvp``. In general that means the memory usage scales with the size of the computation, much like in reverse-mode. (Indeed, :py:func:`linearize` has a similar signature to :py:func:`vjp`!) This function is mainly useful if you want to apply ``f_jvp`` multiple times, i.e. to evaluate a pushforward for many different input tangent vectors at the same linearization point. Moreover if all the input tangent vectors are known at once, it can be more efficient to vectorize using :py:func:`vmap`, as in:: pushfwd = partial(jvp, f, (x,)) y, out_tangents = vmap(pushfwd, out_axes=(None, 0))((in_tangents,)) By using :py:func:`vmap` and :py:func:`jvp` together like this we avoid the stored-linearization memory cost that scales with the depth of the computation, which is incurred by both :py:func:`linearize` and :py:func:`vjp`. Here's a more complete example of using :py:func:`linearize`: >>> import jax >>> import jax.numpy as jnp >>> >>> def f(x): return 3. * jnp.sin(x) + jnp.cos(x / 2.) ... >>> jax.jvp(f, (2.,), (3.,)) (Array(3.26819, dtype=float32, weak_type=True), Array(-5.00753, dtype=float32, weak_type=True)) >>> y, f_jvp = jax.linearize(f, 2.) >>> print(y) 3.2681944 >>> print(f_jvp(3.)) -5.007528 >>> print(f_jvp(4.)) -6.676704 """ check_callable(fun) f = lu.wrap_init(fun) primals_flat, in_tree = tree_flatten(primals) if has_aux: jaxtree_fun, out_tree = flatten_fun_nokwargs2(f, in_tree) else: jaxtree_fun, out_tree = flatten_fun_nokwargs(f, in_tree) out_primals, out_pvals, jaxpr, consts, *maybe_aux = ad.linearize( jaxtree_fun, *primals_flat, has_aux=has_aux) if has_aux: out_tree, aux_tree = out_tree() else: out_tree = out_tree() out_primal_py = tree_unflatten(out_tree, out_primals) primal_avals = list(map(core.get_aval, primals_flat)) # Ensure that lifted_jvp is a PyTree lifted_jvp = Partial(partial(_lift_linearized, jaxpr, primal_avals, (in_tree, out_tree), out_pvals), consts) if has_aux: [aux] = maybe_aux return out_primal_py, lifted_jvp, tree_unflatten(aux_tree, aux) else: [] = maybe_aux return out_primal_py, lifted_jvp
def _lift_linearized(jaxpr, primal_avals, io_tree, out_pvals, consts, *py_args): def fun(*tangents): tangent_avals = list(map(core.get_aval, tangents)) for primal_aval, tangent_aval in zip(primal_avals, tangent_avals): if not core.typecompat(primal_aval.at_least_vspace(), tangent_aval): raise ValueError("linearized function called on tangent values inconsistent with " "the original primal values: " f"got {tangent_aval} for primal aval {primal_aval}") tangents_out = eval_jaxpr(jaxpr, consts, *tangents) tangents_out_ = iter(tangents_out) full_out = [pval.get_known() if pval.is_known() else next(tangents_out_) for pval in out_pvals] assert next(tangents_out_, None) is None return full_out return apply_flat_fun_nokwargs(fun, io_tree, py_args) def _vjp_pullback_wrapper(name, cotangent_dtypes, cotangent_shapes, io_tree, fun, *py_args_): if len(py_args_) != 1: msg = (f"The function returned by `jax.vjp` applied to {name} was called " f"with {len(py_args_)} arguments, but functions returned by " "`jax.vjp` must be called with a single argument corresponding to " f"the single value returned by {name} (even if that returned " "value is a tuple or other container).\n" "\n" "For example, if we have:\n" "\n" " def f(x):\n" " return (x, x)\n" " _, f_vjp = jax.vjp(f, 1.0)\n" "\n" "the function `f` returns a single tuple as output, and so we call " "`f_vjp` with a single tuple as its argument:\n" "\n" " x_bar, = f_vjp((2.0, 2.0))\n" "\n" "If we instead call `f_vjp(2.0, 2.0)`, with the values 'splatted " "out' as arguments rather than in a tuple, this error can arise.") raise TypeError(msg) py_args, = py_args_ in_tree_expected, out_tree = io_tree args, in_tree = tree_flatten(py_args) if in_tree != in_tree_expected: raise TypeError(f"Tree structure of cotangent input {in_tree}, does not match structure of " f"primal output {in_tree_expected}.") for arg, ct_dtype, ct_shape in safe_zip(args, cotangent_dtypes, cotangent_shapes): expected_tangent_dtype = core.primal_dtype_to_tangent_dtype(_dtype(arg)) if expected_tangent_dtype != ct_dtype: raise TypeError( f"Type of cotangent input to vjp pullback function ({ct_dtype}) is not " f"the expected tangent type ({expected_tangent_dtype}) of corresponding primal output " f"with dtype {_dtype(arg)}.") if np.shape(arg) != ct_shape: raise ValueError( f"Shape of cotangent input to vjp pullback function {np.shape(arg)} " "must be the same as the shape of corresponding primal input " f"{ct_shape}.") ans = fun(*args) return tree_unflatten(out_tree, ans) @overload def vjp(fun: Callable[..., T], *primals: Any, has_aux: Literal[False] = False, reduce_axes: Sequence[AxisName] = ()) -> tuple[T, Callable]: ... @overload def vjp(fun: Callable[..., tuple[T, U]], *primals: Any, has_aux: Literal[True], reduce_axes: Sequence[AxisName] = ()) -> tuple[T, Callable, U]: ...
[docs] def vjp( # type: ignore fun: Callable, *primals, has_aux: bool = False, reduce_axes=() ) -> tuple[Any, Callable] | tuple[Any, Callable, Any]: """Compute a (reverse-mode) vector-Jacobian product of ``fun``. :py:func:`grad` is implemented as a special case of :py:func:`vjp`. Args: fun: Function to be differentiated. Its arguments should be arrays, scalars, or standard Python containers of arrays or scalars. It should return an array, scalar, or standard Python container of arrays or scalars. primals: A sequence of primal values at which the Jacobian of ``fun`` should be evaluated. The number of ``primals`` should be equal to the number of positional parameters of ``fun``. Each primal value should be an array, a scalar, or a pytree (standard Python containers) thereof. has_aux: Optional, bool. Indicates whether ``fun`` returns a pair where the first element is considered the output of the mathematical function to be differentiated and the second element is auxiliary data. Default False. Returns: If ``has_aux`` is ``False``, returns a ``(primals_out, vjpfun)`` pair, where ``primals_out`` is ``fun(*primals)``. If ``has_aux`` is ``True``, returns a ``(primals_out, vjpfun, aux)`` tuple where ``aux`` is the auxiliary data returned by ``fun``. ``vjpfun`` is a function from a cotangent vector with the same shape as ``primals_out`` to a tuple of cotangent vectors with the same number and shapes as ``primals``, representing the vector-Jacobian product of ``fun`` evaluated at ``primals``. >>> import jax >>> >>> def f(x, y): ... return jax.numpy.sin(x), jax.numpy.cos(y) ... >>> primals, f_vjp = jax.vjp(f, 0.5, 1.0) >>> xbar, ybar = f_vjp((-0.7, 0.3)) >>> print(xbar) -0.61430776 >>> print(ybar) -0.2524413 """ if reduce_axes: raise NotImplementedError("reduce_axes argument to vjp is deprecated") del reduce_axes check_callable(fun) return _vjp( lu.wrap_init(fun), *primals, has_aux=has_aux)
def _vjp(fun: lu.WrappedFun, *primals, has_aux=False): """Variant of vjp() that takes an lu.WrappedFun.""" primals_flat, in_tree = tree_flatten(primals) for arg in primals_flat: dispatch.check_arg(arg) if not has_aux: flat_fun, out_tree = flatten_fun_nokwargs(fun, in_tree) out_primal, out_vjp = ad.vjp(flat_fun, primals_flat) out_tree = out_tree() else: flat_fun, out_aux_trees = flatten_fun_nokwargs2(fun, in_tree) out_primal, out_vjp, aux = ad.vjp( flat_fun, primals_flat, has_aux=True) out_tree, aux_tree = out_aux_trees() out_primal_py = tree_unflatten(out_tree, out_primal) ct_dtypes = [core.primal_dtype_to_tangent_dtype(_dtype(x)) for x in out_primal] ct_shapes = [np.shape(x) for x in out_primal] # Ensure that vjp_py is a PyTree so that we can pass it from the forward to the # backward pass in a custom VJP. vjp_py = Partial(partial(_vjp_pullback_wrapper, fun.__name__, ct_dtypes, ct_shapes, (out_tree, in_tree)), out_vjp) if not has_aux: return out_primal_py, vjp_py else: return out_primal_py, vjp_py, tree_unflatten(aux_tree, aux)
[docs] def linear_transpose(fun: Callable, *primals, reduce_axes=()) -> Callable: """Transpose a function that is promised to be linear. For linear functions, this transformation is equivalent to :py:func:`vjp`, but avoids the overhead of computing the forward pass. The outputs of the transposed function will always have the exact same dtypes as ``primals``, even if some values are truncated (e.g., from complex to float, or from float64 to float32). To avoid truncation, use dtypes in ``primals`` that match the full range of desired outputs from the transposed function. Integer dtypes are not supported. Args: fun: the linear function to be transposed. *primals: a positional argument tuple of arrays, scalars, or (nested) standard Python containers (tuples, lists, dicts, namedtuples, i.e., pytrees) of those types used for evaluating the shape/dtype of ``fun(*primals)``. These arguments may be real scalars/ndarrays, but that is not required: only the ``shape`` and ``dtype`` attributes are accessed. See below for an example. (Note that the duck-typed objects cannot be namedtuples because those are treated as standard Python containers.) Returns: A callable that calculates the transpose of ``fun``. Valid input into this function must have the same shape/dtypes/structure as the result of ``fun(*primals)``. Output will be a tuple, with the same shape/dtypes/structure as ``primals``. >>> import jax >>> import types >>> >>> f = lambda x, y: 0.5 * x - 0.5 * y >>> scalar = types.SimpleNamespace(shape=(), dtype=np.dtype(np.float32)) >>> f_transpose = jax.linear_transpose(f, scalar, scalar) >>> f_transpose(1.0) (Array(0.5, dtype=float32), Array(-0.5, dtype=float32)) """ if reduce_axes: raise NotImplementedError("reduce_axes argument to transpose is deprecated") del reduce_axes primals_flat, in_tree = tree_flatten(primals) flat_fun, out_tree = flatten_fun_nokwargs(lu.wrap_init(fun), in_tree) in_avals = map(shaped_abstractify, primals_flat) in_dtypes = map(dtypes.dtype, in_avals) in_pvals = map(pe.PartialVal.unknown, in_avals) jaxpr, out_pvals, const = pe.trace_to_jaxpr_nounits(flat_fun, in_pvals, instantiate=True) jaxpr, _ = pe.dce_jaxpr(jaxpr, [True] * len(jaxpr.outvars), True) out_avals, _ = unzip2(out_pvals) out_dtypes = map(dtypes.dtype, out_avals) if not (all(dtypes.issubdtype(d, np.inexact) for d in in_dtypes + out_dtypes) or all(dtypes.issubdtype(d, np.integer) for d in in_dtypes + out_dtypes)): raise TypeError("linear_transpose only supports [float or complex] -> " "[float or complex], and integer -> integer functions, " f"but got {in_dtypes} -> {out_dtypes}.") @api_boundary def transposed_fun(const, out_cotangent): out_cts, out_tree2 = tree_flatten(out_cotangent) if out_tree() != out_tree2: raise TypeError("cotangent tree does not match function output, " f"expected {out_tree()} but got {out_tree2}") if not all(map(core.typecheck, out_avals, out_cts)): raise TypeError("cotangent type does not match function output, " f"expected {out_avals} but got {out_cts}") dummies = [ad.UndefinedPrimal(a) for a in in_avals] in_cts = ad.backward_pass(jaxpr, True, const, dummies, out_cts) in_cts = map(ad.instantiate_zeros, in_cts) return tree_unflatten(in_tree, in_cts) # Ensure that transposed_fun is a PyTree return Partial(transposed_fun, const)
def _flat_axes_specs(abstracted_axes, *args, **kwargs ) -> list[pe.AbstractedAxesSpec]: if kwargs: raise NotImplementedError def ax_leaf(l): return (isinstance(l, dict) and all_leaves(l.values()) or isinstance(l, tuple) and all_leaves(l, lambda x: x is None)) return broadcast_prefix(abstracted_axes, args, ax_leaf) # TODO(phawkins): for some reason mypy cannot determine these overloads are # non-overlapping. Pytype is happy with them. @overload def make_jaxpr(fun: Callable, # type: ignore static_argnums: int | Iterable[int] = (), axis_env: Sequence[tuple[AxisName, int]] | None = None, return_shape: Literal[False] = ..., abstracted_axes: Any | None = None, ) -> Callable[..., core.ClosedJaxpr]: ... @overload def make_jaxpr(fun: Callable, # type: ignore static_argnums: int | Iterable[int] = (), axis_env: Sequence[tuple[AxisName, int]] | None = None, return_shape: Literal[True] = ..., abstracted_axes: Any | None = None, ) -> Callable[..., tuple[core.ClosedJaxpr, Any]]: ...
[docs] def make_jaxpr(fun: Callable, static_argnums: int | Iterable[int] = (), axis_env: Sequence[tuple[AxisName, int]] | None = None, return_shape: bool = False, abstracted_axes: Any | None = None, ) -> Callable[..., (core.ClosedJaxpr | tuple[core.ClosedJaxpr, Any])]: """Creates a function that produces its jaxpr given example args. Args: fun: The function whose ``jaxpr`` is to be computed. Its positional arguments and return value should be arrays, scalars, or standard Python containers (tuple/list/dict) thereof. static_argnums: See the :py:func:`jax.jit` docstring. axis_env: Optional, a sequence of pairs where the first element is an axis name and the second element is a positive integer representing the size of the mapped axis with that name. This parameter is useful when lowering functions that involve parallel communication collectives, and it specifies the axis name/size environment that would be set up by applications of :py:func:`jax.pmap`. return_shape: Optional boolean, defaults to ``False``. If ``True``, the wrapped function returns a pair where the first element is the XLA computation and the second element is a pytree with the same structure as the output of ``fun`` and where the leaves are objects with ``shape``, ``dtype``, and ``named_shape`` attributes representing the corresponding types of the output leaves. Returns: A wrapped version of ``fun`` that when applied to example arguments returns a ``ClosedJaxpr`` representation of ``fun`` on those arguments. If the argument ``return_shape`` is ``True``, then the returned function instead returns a pair where the first element is the ``ClosedJaxpr`` representation of ``fun`` and the second element is a pytree representing the structure, shape, dtypes, and named shapes of the output of ``fun``. A ``jaxpr`` is JAX's intermediate representation for program traces. The ``jaxpr`` language is based on the simply-typed first-order lambda calculus with let-bindings. :py:func:`make_jaxpr` adapts a function to return its ``jaxpr``, which we can inspect to understand what JAX is doing internally. The ``jaxpr`` returned is a trace of ``fun`` abstracted to :py:class:`ShapedArray` level. Other levels of abstraction exist internally. We do not describe the semantics of the ``jaxpr`` language in detail here, but instead give a few examples. >>> import jax >>> >>> def f(x): return jax.numpy.sin(jax.numpy.cos(x)) >>> print(f(3.0)) -0.83602 >>> jax.make_jaxpr(f)(3.0) { lambda ; a:f32[]. let b:f32[] = cos a; c:f32[] = sin b in (c,) } >>> jax.make_jaxpr(jax.grad(f))(3.0) { lambda ; a:f32[]. let b:f32[] = cos a c:f32[] = sin a _:f32[] = sin b d:f32[] = cos b e:f32[] = mul 1.0 d f:f32[] = neg e g:f32[] = mul f c in (g,) } """ check_callable(fun) static_argnums = _ensure_index_tuple(static_argnums) def abstractify(args, kwargs): flat_args, in_tree = tree_flatten((args, kwargs)) if abstracted_axes is None: return map(shaped_abstractify, flat_args), in_tree, [True] * len(flat_args) else: axes_specs = _flat_axes_specs(abstracted_axes, *args, **kwargs) in_type = pe.infer_lambda_input_type(axes_specs, flat_args) in_avals, keep_inputs = unzip2(in_type) return in_avals, in_tree, keep_inputs @wraps(fun) @api_boundary def make_jaxpr_f(*args, **kwargs): f = lu.wrap_init(fun) if static_argnums: dyn_argnums = [i for i in range(len(args)) if i not in static_argnums] f, args = argnums_partial(f, dyn_argnums, args) in_avals, in_tree, keep_inputs = abstractify(args, kwargs) in_type = tuple(zip(in_avals, keep_inputs)) f, out_tree = flatten_fun(f, in_tree) f = lu.annotate(f, in_type) debug_info = pe.debug_info(fun, in_tree, out_tree, True, 'make_jaxpr') with ExitStack() as stack: for axis_name, size in axis_env or []: stack.enter_context(core.extend_axis_env(axis_name, size, None)) jaxpr, out_type, consts = pe.trace_to_jaxpr_dynamic2( f, debug_info=debug_info) closed_jaxpr = core.ClosedJaxpr(jaxpr, consts) if return_shape: out_avals, _ = unzip2(out_type) out_shapes_flat = [ ShapeDtypeStruct(a.shape, a.dtype, a.named_shape) for a in out_avals] return closed_jaxpr, tree_unflatten(out_tree(), out_shapes_flat) return closed_jaxpr make_jaxpr_f.__module__ = "jax" if hasattr(fun, "__qualname__"): make_jaxpr_f.__qualname__ = f"make_jaxpr({fun.__qualname__})" if hasattr(fun, "__name__"): make_jaxpr_f.__name__ = f"make_jaxpr({fun.__name__})" return make_jaxpr_f
def _infer_src_sharding(src, x) -> Sharding | None: if src is not None: return src if isinstance(x, array.ArrayImpl): return x.sharding elif isinstance(x, core.Tracer): aval = core.get_aval(x) if isinstance(aval, ConcreteArray) and isinstance(aval.val, array.ArrayImpl): return aval.val.sharding return None # TODO(yashkatariya): Generalize is_compatible_aval (maybe renamed) and use that # to check if shardings are compatible with the input. def _check_sharding(x, s): if isinstance(s, Sharding): aval = shaped_abstractify(x) if isinstance(s, XLACompatibleSharding) and not isinstance(s, PmapSharding): pjit.pjit_check_aval_sharding( (s,), (aval,), None, "device_put args", allow_uneven_sharding=False) s.shard_shape(aval.shape) # should raise an Error if incompatible
[docs] def device_put( x, device: None | xc.Device | Sharding | Any | TransferToMemoryKind = None, *, src: None | xc.Device | Sharding | Any | TransferToMemoryKind = None): """Transfers ``x`` to ``device``. Args: x: An array, scalar, or (nested) standard Python container thereof. device: The (optional) :py:class:`Device`, `Sharding`, or a (nested) `Sharding` in standard Python container (must be a tree prefix of ``x``), representing the device(s) to which ``x`` should be transferred. If given, then the result is committed to the device(s). Returns: A copy of ``x`` that resides on ``device``. If the ``device`` parameter is ``None``, then this operation behaves like the identity function if the operand is on any device already, otherwise it transfers the data to the default device, uncommitted. For more details on data placement see the :ref:`FAQ on data placement <faq-data-placement>`. This function is always asynchronous, i.e. returns immediately without blocking the calling Python thread until any transfers are completed. """ with config.explicit_device_put_scope(): if ((device is None or isinstance(device, (xc.Device, Sharding, TransferToMemoryKind))) and (src is None or isinstance(src, (xc.Device, Sharding, TransferToMemoryKind)))): for leaf in tree_leaves(x): _check_sharding(leaf, s=device) return tree_map( lambda y: dispatch.device_put_p.bind( y, device=device, src=_infer_src_sharding(src, y)), x) x_flat, treedef = tree_flatten(x) device_flat = flatten_axes("device_put device", treedef, device) src_flat = flatten_axes("device_put source", treedef, src) for x_leaf, device_leaf in zip(x_flat, device_flat): _check_sharding(x_leaf, device_leaf) out_flat = [ dispatch.device_put_p.bind(xf, device=d, src=_infer_src_sharding(s, xf)) for xf, d, s in zip(x_flat, device_flat, src_flat) ] return tree_unflatten(treedef, out_flat)
[docs] def device_put_sharded(shards: Sequence[Any], devices: Sequence[xc.Device]): # noqa: F811 """Transfer array shards to specified devices and form Array(s). Args: shards: A sequence of arrays, scalars, or (nested) standard Python containers thereof representing the shards to be stacked together to form the output. The length of ``shards`` must equal the length of ``devices``. devices: A sequence of :py:class:`Device` instances representing the devices to which corresponding shards in ``shards`` will be transferred. This function is always asynchronous, i.e. returns immediately. Returns: A Array or (nested) Python container thereof representing the elements of ``shards`` stacked together, with each shard backed by physical device memory specified by the corresponding entry in ``devices``. Examples: Passing a list of arrays for ``shards`` results in a sharded array containing a stacked version of the inputs: >>> import jax >>> devices = jax.local_devices() >>> x = [jax.numpy.ones(5) for device in devices] >>> y = jax.device_put_sharded(x, devices) >>> np.allclose(y, jax.numpy.stack(x)) True Passing a list of nested container objects with arrays at the leaves for ``shards`` corresponds to stacking the shards at each leaf. This requires all entries in the list to have the same tree structure: >>> x = [(i, jax.numpy.arange(i, i + 4)) for i in range(len(devices))] >>> y = jax.device_put_sharded(x, devices) >>> type(y) <class 'tuple'> >>> y0 = jax.device_put_sharded([a for a, b in x], devices) >>> y1 = jax.device_put_sharded([b for a, b in x], devices) >>> np.allclose(y[0], y0) True >>> np.allclose(y[1], y1) True See Also: - device_put - device_put_replicated """ # TODO(jakevdp): provide a default for devices that considers both local # devices and pods if not isinstance(shards, Sequence): raise ValueError("device_put_sharded `shards` input must be a sequence; " f"got {type(shards)}") if len(shards) != len(devices): raise ValueError(f"len(shards) = {len(shards)} must equal " f"len(devices) = {len(devices)}.") def _device_put_sharded(*xs): avals = [core.raise_to_shaped(core.get_aval(x)) for x in xs] if not all(a1 == a2 for a1, a2 in zip(avals[:-1], avals[1:])): a1, a2 = next((a1, a2) for a1, a2 in zip(avals[:-1], avals[1:]) if a1 != a2) raise ValueError("the shards passed to device_put_sharded must have " f"consistent shape and dtype, but got {a1} and {a2}.") stacked_aval = avals[0].update(shape=(len(devices),) + avals[0].shape) sharding_spec = sharding_specs.create_pmap_sharding_spec(stacked_aval.shape) sharding = PmapSharding(np.array(devices), sharding_spec) if dtypes.issubdtype(stacked_aval.dtype, dtypes.extended): return stacked_aval.dtype._rules.device_put_sharded(xs, stacked_aval, sharding, devices) if config.pmap_no_rank_reduction.value: ys = [] for x in xs: if not isinstance(x, (np.ndarray, basearray.Array)): x = np.asarray(x) ys.append(x[None]) else: ys = xs return pxla.batched_device_put(stacked_aval, sharding, ys, list(devices)) with config.explicit_device_put_scope(): return tree_map(_device_put_sharded, *shards)
[docs] def device_put_replicated(x: Any, devices: Sequence[xc.Device]): # noqa: F811 """Transfer array(s) to each specified device and form Array(s). Args: x: an array, scalar, or (nested) standard Python container thereof representing the array to be replicated to form the output. devices: A sequence of :py:class:`Device` instances representing the devices to which ``x`` will be transferred. This function is always asynchronous, i.e. returns immediately. Returns: An Array or (nested) Python container thereof representing the value of ``x`` broadcasted along a new leading axis of size ``len(devices)``, with each slice along that new leading axis backed by memory on the device specified by the corresponding entry in ``devices``. Examples: Passing an array: >>> import jax >>> devices = jax.local_devices() >>> x = jax.numpy.array([1., 2., 3.]) >>> y = jax.device_put_replicated(x, devices) >>> np.allclose(y, jax.numpy.stack([x for _ in devices])) True See Also: - device_put - device_put_sharded """ if not isinstance(devices, Sequence) or not devices: raise ValueError("`devices` argument to `device_put_replicated must be " "a non-empty sequence.") def _device_put_replicated(x): aval = core.unmapped_aval(len(devices), core.no_axis_name, 0, core.raise_to_shaped(core.get_aval(x))) assert isinstance(aval, ShapedArray) sharding_spec = sharding_specs.create_pmap_sharding_spec(aval.shape) if config.pmap_no_rank_reduction.value: if isinstance(x, (np.ndarray, basearray.Array)): buf = device_put(x[None], devices[0]) else: buf = device_put(x, devices[0])[None] else: buf = device_put(x, devices[0]) sharding = PmapSharding(np.array(devices), sharding_spec) if dtypes.issubdtype(aval.dtype, dtypes.extended): return aval.dtype._rules.device_put_replicated(buf, aval, sharding, devices) assert len(xla.aval_to_xla_shapes(aval)) == 1 return pxla.batched_device_put(aval, sharding, [buf] * len(devices), devices) with config.explicit_device_put_scope(): return tree_map(_device_put_replicated, x)
# TODO(mattjj): consider revising def _device_get(x): if isinstance(x, core.Tracer): return x try: toarray = x.__array__ except AttributeError: return x else: return toarray()
[docs] def device_get(x: Any): """Transfer ``x`` to host. If ``x`` is a pytree, then the individual buffers are copied in parallel. Args: x: An array, scalar, Array or (nested) standard Python container thereof representing the array to be transferred to host. Returns: An array or (nested) Python container thereof representing the value of ``x``. Examples: Passing a Array: >>> import jax >>> x = jax.numpy.array([1., 2., 3.]) >>> jax.device_get(x) array([1., 2., 3.], dtype=float32) Passing a scalar (has no effect): >>> jax.device_get(1) 1 See Also: - device_put - device_put_sharded - device_put_replicated """ with config.explicit_device_get_scope(): for y in tree_leaves(x): try: y.copy_to_host_async() except AttributeError: pass return tree_map(_device_get, x)
[docs] class ShapeDtypeStruct: """A container for the shape, dtype, and other static attributes of an array. ``ShapeDtypeStruct`` is often used in conjunction with :func:`jax.eval_shape`. Args: shape: a sequence of integers representing an array shape dtype: a dtype-like object named_shape: (optional) a dictionary representing a named shape sharding: (optional) a :class:`jax.Sharding` object """ __slots__ = ["shape", "dtype", "named_shape", "sharding"]
[docs] def __init__(self, shape, dtype, named_shape=None, sharding=None): self.shape = tuple(shape) if dtype is None: raise ValueError("ShapeDtypeStruct: dtype must be specified.") self.dtype = dtype if dtypes.issubdtype(dtype, dtypes.extended) else np.dtype(dtype) if sharding is not None and not isinstance(sharding, Sharding): raise ValueError( "sharding should be an instance of `jax.sharding.Sharding`. " f"Got {sharding} of type {type(sharding)}.") self.sharding = sharding self.named_shape = {} if named_shape is None else dict(named_shape)
size = property(lambda self: math.prod(self.shape)) ndim = property(lambda self: len(self.shape)) def __len__(self): try: return self.shape[0] except IndexError as e: raise TypeError("len() of unsized object") from e # same as numpy error def __repr__(self): ns = f", named_shape={self.named_shape}" if self.named_shape else "" sh = f", sharding={self.sharding}" if self.sharding is not None else "" return (f"{type(self).__name__}(shape={self.shape}, " f"dtype={self.dtype.name}{ns}{sh})") __str__ = __repr__ def __eq__(self, other): if not isinstance(other, ShapeDtypeStruct): return False else: return ((other.shape, other.dtype, other.named_shape, other.sharding) == (self.shape, self.dtype, self.named_shape, self.sharding)) def __hash__(self): # TODO(frostig): avoid the conversion from dict by addressing # https://github.com/google/jax/issues/8182 named = frozenset(self.named_shape.items()) return hash((self.shape, self.dtype, named, self.sharding))
core.pytype_aval_mappings[ShapeDtypeStruct] = ( lambda x: ShapedArray(x.shape, dtypes.canonicalize_dtype(x.dtype, allow_extended_dtype=True), weak_type=False, named_shape=x.named_shape))
[docs] @api_boundary def eval_shape(fun: Callable, *args, **kwargs): """Compute the shape/dtype of ``fun`` without any FLOPs. This utility function is useful for performing shape inference. Its input/output behavior is defined by:: def eval_shape(fun, *args, **kwargs): out = fun(*args, **kwargs) shape_dtype_struct = lambda x: jax.ShapeDtypeStruct(x.shape, x.dtype) return jax.tree_util.tree_map(shape_dtype_struct, out) But instead of applying ``fun`` directly, which might be expensive, it uses JAX's abstract interpretation machinery to evaluate the shapes without doing any FLOPs. Using :py:func:`eval_shape` can also catch shape errors, and will raise same shape errors as evaluating ``fun(*args, **kwargs)``. Args: fun: The function whose output shape should be evaluated. *args: a positional argument tuple of arrays, scalars, or (nested) standard Python containers (tuples, lists, dicts, namedtuples, i.e. pytrees) of those types. Since only the ``shape`` and ``dtype`` attributes are accessed, one can use :class:`jax.ShapeDtypeStruct` or another container that duck-types as ndarrays (note however that duck-typed objects cannot be namedtuples because those are treated as standard Python containers). **kwargs: a keyword argument dict of arrays, scalars, or (nested) standard Python containers (pytrees) of those types. As in ``args``, array values need only be duck-typed to have ``shape`` and ``dtype`` attributes. Returns: out: a nested PyTree containing :class:`jax.ShapeDtypeStruct` objects as leaves. For example: >>> import jax >>> import jax.numpy as jnp >>> >>> f = lambda A, x: jnp.tanh(jnp.dot(A, x)) >>> A = jax.ShapeDtypeStruct((2000, 3000), jnp.float32) >>> x = jax.ShapeDtypeStruct((3000, 1000), jnp.float32) >>> out = jax.eval_shape(f, A, x) # no FLOPs performed >>> print(out.shape) (2000, 1000) >>> print(out.dtype) float32 All arguments passed via :func:`eval_shape` will be treated as dynamic; static arguments can be included via closure, for example using :func:`functools.partial`: >>> import jax >>> from jax import lax >>> from functools import partial >>> import jax.numpy as jnp >>> >>> x = jax.ShapeDtypeStruct((1, 1, 28, 28), jnp.float32) >>> kernel = jax.ShapeDtypeStruct((32, 1, 3, 3), jnp.float32) >>> >>> conv_same = partial(lax.conv_general_dilated, window_strides=(1, 1), padding="SAME") >>> out = jax.eval_shape(conv_same, x, kernel) >>> print(out.shape) (1, 32, 28, 28) >>> print(out.dtype) float32 """ try: hash(fun) except TypeError: fun = partial(fun) return jit(fun).eval_shape(*args, **kwargs)
[docs] def named_call( fun: F, *, name: str | None = None, ) -> F: """Adds a user specified name to a function when staging out JAX computations. When staging out computations for just-in-time compilation to XLA (or other backends such as TensorFlow) JAX runs your Python program but by default does not preserve any of the function names or other metadata associated with it. This can make debugging the staged out (and/or compiled) representation of your program complicated because there is limited context information for each operation being executed. `named_call` tells JAX to stage the given function out as a subcomputation with a specific name. When the staged out program is compiled with XLA these named subcomputations are preserved and show up in debugging utilities like the TensorFlow Profiler in TensorBoard. Names are also preserved when staging out JAX programs to TensorFlow using :func:`experimental.jax2tf.convert`. Args: fun: Function to be wrapped. This can be any Callable. name: Optional. The prefix to use to name all sub computations created within the name scope. Use the fun.__name__ if not specified. Returns: A version of `fun` that is wrapped in a name_scope. """ if name is None: name = fun.__name__ return source_info_util.extend_name_stack(name)(fun)
[docs] @contextmanager def named_scope( name: str, ) -> Generator[None, None, None]: """A context manager that adds a user specified name to the JAX name stack. When staging out computations for just-in-time compilation to XLA (or other backends such as TensorFlow) JAX does not, by default, preserve the names (or other source metadata) of Python functions it encounters. This can make debugging the staged out (and/or compiled) representation of your program complicated because there is limited context information for each operation being executed. ``named_scope`` tells JAX to stage the given function with additional annotations on the underlying operations. JAX internally keeps track of these annotations in a name stack. When the staged out program is compiled with XLA these annotations are preserved and show up in debugging utilities like the TensorFlow Profiler in TensorBoard. Names are also preserved when staging out JAX programs to TensorFlow using :func:`experimental.jax2tf.convert`. Args: name: The prefix to use to name all operations created within the name scope. Yields: Yields ``None``, but enters a context in which `name` will be appended to the active name stack. Examples: ``named_scope`` can be used as a context manager inside compiled functions: >>> import jax >>> >>> @jax.jit ... def layer(w, x): ... with jax.named_scope("dot_product"): ... logits = w.dot(x) ... with jax.named_scope("activation"): ... return jax.nn.relu(logits) It can also be used as a decorator: >>> @jax.jit ... @jax.named_scope("layer") ... def layer(w, x): ... logits = w.dot(x) ... return jax.nn.relu(logits) """ if not isinstance(name, str): raise ValueError("named_scope name argument must be a string.") with source_info_util.extend_name_stack(name): yield
def effects_barrier(): """Waits until existing functions have completed any side-effects.""" dispatch.runtime_tokens.block_until_ready()
[docs] def block_until_ready(x): """ Tries to call a ``block_until_ready`` method on pytree leaves. Args: x: a pytree, usually with at least some JAX array instances at its leaves. Returns: A pytree with the same structure and values of the input, where the values of all JAX array leaves are ready. """ def try_to_block(x): try: return x.block_until_ready() except AttributeError: return x return tree_map(try_to_block, x)
def clear_backends(): """ Clear all backend clients so that new backend clients can be created later. """ xb._clear_backends() xb.local_devices.cache_clear() xb.process_count.cache_clear() dispatch.xla_primitive_callable.cache_clear() pjit._pjit_lower_cached.cache_clear() pjit._create_pjit_jaxpr.cache_clear() # pytype: disable=attribute-error pjit._cpp_pjit_cache.clear() xc._xla.PjitFunctionCache.clear_all()
[docs] def live_arrays(platform=None): """Return all live arrays in the backend for `platform`. If platform is None, it is the default backend. """ return xb.get_backend(platform).live_arrays()
[docs] def clear_caches(): """Clear all compilation and staging caches.""" # Clear all lu.cache and util.weakref_lru_cache instances (used for staging # and Python-dispatch compiled executable caches). lu.clear_all_caches() util.clear_all_weakref_lru_caches() # Clear all C++ compiled executable caches for pjit pjit._cpp_pjit_cache.clear() xc._xla.PjitFunctionCache.clear_all() # Clear all C++ compiled executable caches for pmap for fun in _pmap_cache_clears: fun._cache_clear() # Clear particular util.cache instances. dispatch.xla_primitive_callable.cache_clear()