# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
#
# 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
#
# http://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.
# ==============================================================================
"""Script Language Operators."""
# pylint: disable=g-bad-name
import threading
# Used by py_util.cc to get tracebacks.
import traceback # pylint: disable=unused-import
import weakref
import numpy as np
from tensorflow.python.eager import backprop
from tensorflow.python.eager import backprop_util
from tensorflow.python.eager import context
from tensorflow.python.eager import tape as tape_lib
from tensorflow.python.framework import composite_tensor
from tensorflow.python.framework import constant_op
from tensorflow.python.framework import dtypes
from tensorflow.python.framework import func_graph
from tensorflow.python.framework import function
from tensorflow.python.framework import ops
from tensorflow.python.framework import tensor_spec
from tensorflow.python.framework import type_spec
from tensorflow.python.lib.core import _pywrap_py_func
from tensorflow.python.ops import gen_script_ops
from tensorflow.python.ops import resource_variable_ops
from tensorflow.python.util import compat
from tensorflow.python.util import deprecation
from tensorflow.python.util import dispatch
from tensorflow.python.util import lazy_loader
from tensorflow.python.util import nest
from tensorflow.python.util import tf_inspect
from tensorflow.python.util.tf_export import tf_export
autograph = lazy_loader.LazyLoader(
"autograph", globals(),
"tensorflow.python.autograph.impl.api")
# Map from EagerPyFunc token to tuple (tape, eager args, eager outputs);
# used for differentiation.
tape_cache = {}
def _maybe_copy_to_context_device(tensor, device_name):
"""Copy an EagerTensor to the current device if it's not on `device_name`."""
in_device = tensor.backing_device
if device_name == in_device:
return tensor
else:
# Note that EagerTensor._copy bypasses the placer and copies to the context
# device, which means e.g. int32 Tensors which would normally be forced onto
# the CPU can instead be placed on the GPU. This is necessary so that the
# PyFunc kernel always returns Tensors on the device it's executing on.
return tensor._copy() # pylint: disable=protected-access
class EagerFunc:
"""A wrapper for a function owned by an EagerPyFunc."""
def __init__(self, func, Tout, is_grad_func):
"""Constructs an EagerFunc.
Args:
func: The function to wrap.
Tout: A list of datatypes for the output; an empty list if the output is
None.
is_grad_func: Whether this EagerFunc is the gradient of another
EagerPyFunc.
"""
self._func = func
self._out_dtypes = Tout
self._is_grad_func = is_grad_func
self._support_graph_mode_gradient = False
def set_support_graph_mode_gradient(self):
"""Indicates the object shall support gradient ops.
This function is internally used by _EagerPyFuncGrad to support
graph mode gradient of EagerFunc via tf.gradient().
"""
self._support_graph_mode_gradient = True
def _convert(self, value, dtype):
"""Converts `value` to a tensor of type `dtype`, with error checking.
Args:
value: The tensor to convert.
dtype: The desired dtype.
Returns:
A tensor of type `dtype`, or a zeros tensor if value is None and
this function is in fact a gradient function.
Raises:
RuntimeError: if `value` is a variable.
"""
if isinstance(value, resource_variable_ops.ResourceVariable):
raise RuntimeError(
"Attempting to return a variable from an eagerly executed py_func. "
"Only numeric data structures like Tensors or NumPy arrays should "
"be returned; to return the value of a variable, make sure to obtain "
"the Tensor backing it by calling `.read_value()` on the variable in "
f"question: {value}")
if value is None and self._is_grad_func:
# Gradient functions may legitimately return a list that contains
# both Tensors and Python Nones. Unfortunately this breaks the
# OpKernel, so for now we replace None objects with zeros, which is
# mathematically correct but will prevent short-circuiting gradient
# computations.
#
# TODO(akshayka): Make it possible to return a list of both Tensors and
# Nones from an EagerPyFunc.
return constant_op.constant(0.0, dtype=dtype)
return ops.convert_to_tensor(value, dtype=dtype)
def __call__(self, device, token, args):
"""Calls `self._func` in eager mode, recording the tape if needed."""
use_tape_cache = (
self._support_graph_mode_gradient or tape_lib.could_possibly_record())
if use_tape_cache:
with backprop.GradientTape() as tape:
for tensor in args:
for t in nest.flatten(tensor):
if backprop_util.IsTrainable(t):
tape.watch(t)
outputs = self._call(device, args)
tape_cache[compat.as_bytes(token)] = (tape, args, outputs)
else:
outputs = self._call(device, args)
return outputs
def _call(self, device, args):
"""Passes `args` to `self._func`, which is executed eagerly."""
with context.eager_mode():
ret = self._func(*args)
# copy the returned tensors to the PyFunc op's device if necessary.
device_name = device
if device_name is None:
# "None" here means "CPU", from the nullptr convention with C++ device
# pointers.
device_name = "/job:localhost/replica:0/task:0/device:CPU:0"
with ops.device(device):
if isinstance(ret, (tuple, list)):
outputs = [
_maybe_copy_to_context_device(self._convert(x, dtype=dtype),
device_name)
for (x, dtype) in zip(ret, self._out_dtypes)
]
elif ret is None:
outputs = None
else:
outputs = _maybe_copy_to_context_device(
self._convert(ret, dtype=self._out_dtypes[0]), device_name)
return outputs
class FuncRegistry:
"""A helper class to keep track of registered py functions.
FuncRegistry keeps a map from unique tokens (string) to python
functions, which takes numpy arrays and outputs numpy arrays.
"""
def __init__(self):
self._lock = threading.Lock()
self._unique_id = 0 # GUARDED_BY(self._lock)
# Only store weakrefs to the functions. The strong reference is stored in
# the graph.
self._funcs = weakref.WeakValueDictionary()
@property
def _ctx(self):
# N.B. This is needed to support calling py_func with GPU tensors,
# which must be transferred to CPU if used in any of the NumPy APIs.
context.ensure_initialized()
return context.context()._handle # pylint: disable=protected-access
def insert(self, func):
"""Registers `func` and returns a unique token for this entry."""
token = self._next_unique_token()
# Store a weakref to the function
self._funcs[token] = func
return token
def remove(self, token):
"""Removes the registered function corresponding to `token`."""
self._funcs.pop(token, None)
def get(self, token, default=None):
"""Gets the registered function corresponding to `token`."""
return self._funcs.get(token, default)
@staticmethod
def _convert(value, dtype=None):
"""Converts an arg to numpy, avoiding dangerous string and unicode dtypes.
Numpy pads with zeros when using string and unicode dtypes if different
components of a tensor have different lengths. This is bad: ignoring the
padding is wrong for text data, and removing the padding is wrong for binary
data. To avoid this bug, we redo the conversion using an object dtype.
Additionally, we convert unicode strings to (byte-)strings for
compatibility.
Args:
value: Value to convert to a numpy array.
dtype: (Optional.) Desired NumPy type for the returned value.
Returns:
A numpy array.
"""
result = np.asarray(value, dtype=dtype, order="C")
if result.dtype.char == "S" and result is not value:
return np.asarray(value, order="C", dtype=object)
elif result.dtype.char == "U" and result is not value:
value = np.vectorize(lambda x: x.encode("utf8"))(value)
return np.asarray(value, order="C", dtype=object)
elif result.dtype.char == "U":
return result.astype(np.bytes_)
else:
return result
def __call__(self, token, device, args):
"""Calls the registered function for `token` with args.
Args:
token: A key into this `FuncRegistry` identifying which function to call.
device: Name of the device on which outputs of `token`'s corresponding
operation should be placed. Used iff the function registered for `token`
is an EagerPyFunc.
args: The arguments to pass to the function registered for `token`.
Returns:
The output of the function registered for `token`.
Raises:
ValueError: if no function is registered for `token`.
"""
func = self.get(token, None)
if func is None:
raise ValueError(f"Could not find callback with key={token} in the "
"registry.")
if isinstance(func, EagerFunc):
# NB: Different invocations of the same py_func will share the same
# token, and the entries they stash in the tape_cache will collide.
# In practice, when executing a graph, this should only happen if
# the py_func is in a while_loop whose iterations are run in parallel
# or if the graph is being driven by concurrent session.run() calls.
#
# TODO(akshayka): Key the tape cache in a thread-safe way.
return func(device, token, args)
else:
ret = func(*args)
# Strings seem to lead to a memory leak here if they're not wrapped in a
# list.
if isinstance(ret, bytes):
ret = [ret]
# Ensures that we return either a single numpy array or a list of numpy
# arrays.
if isinstance(ret, (tuple, list)):
return [self._convert(x) for x in ret]
else:
return self._convert(ret)
def size(self):
"""Returns how many functions are currently registered."""
return len(self._funcs)
def _next_unique_token(self):
"""Returns a unique token."""
with self._lock:
uid = self._unique_id
self._unique_id += 1
return "pyfunc_%d" % uid
# Global registry for py functions.
_py_funcs = FuncRegistry()
_pywrap_py_func.initialize_py_trampoline(_py_funcs)
def _internal_py_func(func,
inp,
Tout,
stateful=None,
use_eager_py_func=False,
is_grad_func=False,
name=None):
"""See documentation for py_func and eager_py_func."""
if not callable(func):
raise ValueError(
f"Expected func to be callable. Received func={func} of type "
f"{type(func)}.")
original_func = func
func = autograph.do_not_convert(func)
inp = list(inp)
# Normalize Tout.
is_list_or_tuple = isinstance(Tout, (list, tuple))
Tout = Tout if is_list_or_tuple else [Tout]
Tout = [_as_dtype_or_type_spec(t) for t in Tout]
# Check if we need to handle CompositeTensor inputs or outputs.
handle_composite_tensors = (
use_eager_py_func and
(any(isinstance(v, composite_tensor.CompositeTensor) for v in inp) or
any(isinstance(t, type_spec.TypeSpec) for t in Tout)))
if handle_composite_tensors:
func, inp, Tout, out_structure = _wrap_for_composites(func, inp, Tout)
if use_eager_py_func:
func = EagerFunc(func, Tout, is_grad_func)
# Tying the registered function's lifetime with the current default graph is
# not reliable. For example, Estimator-based binaries may switch graphs in
# between model training end evaluation, via saved_model. Those binaries work
# because the original function is global, and break once the registered
# function is an anonymous lambda, like the one produced by do_not_convert.
# To avoid breaking those cases, we attach the wrapper to the original
# function so that their lifetime is connected.
# TODO(b/144286616): Remove this.
if tf_inspect.isfunction(original_func):
# Note: this check is needed because original_func may be a descriptor
# (https://docs.python.org/3/howto/descriptor.html)
# and we can't attach attributes to those.
original_func.ag_dnc_wrapper__ = func
token = _py_funcs.insert(func)
# We tie the registered function's lifetime with the current default graph,
# i.e., when the current graph is destroyed, we remove its py funcs.
graph = ops.get_default_graph()
while True:
current_graph = graph
if isinstance(graph, function._FuncGraph): # pylint: disable=protected-access
graph = graph._outer_graph # pylint: disable=protected-access
elif isinstance(graph, func_graph.FuncGraph):
graph = graph.outer_graph
if graph is current_graph:
break
# TODO(zhifengc): Consider adding a Graph method to collect
# `cleanup` objects in one of its member.
if not hasattr(graph, "_py_funcs_used_in_graph"):
graph._py_funcs_used_in_graph = [] # pylint: disable=protected-access
# Store a reference to the function in the graph to ensure it stays alive
# as long as the graph lives. When the graph is destroyed, the function
# is left to the garbage collector for destruction as well.
graph._py_funcs_used_in_graph.append(func) # pylint: disable=protected-access
if use_eager_py_func:
result = gen_script_ops.eager_py_func(
input=inp,
token=token,
is_async=context.is_async(),
Tout=Tout,
name=name)
else:
if stateful:
result = gen_script_ops.py_func(
input=inp, token=token, Tout=Tout, name=name)
else:
result = gen_script_ops.py_func_stateless(
input=inp, token=token, Tout=Tout, name=name)
if handle_composite_tensors and Tout:
result = nest.pack_sequence_as(
out_structure, result, expand_composites=True)
return result if is_list_or_tuple else result[0]
# TODO(akshayka): Implement higher-order derivatives.
@ops.RegisterGradient("EagerPyFunc")
def _EagerPyFuncGrad(op, *dy):
"""Computes the gradient of an EagerPyFunc."""
token = op.get_attr("token")
def eagerly_executed_grad(*dy):
tape, eager_inputs, eager_outputs = tape_cache.pop(compat.as_bytes(token))
return tape.gradient(eager_outputs, eager_inputs, output_gradients=dy)
with ops.control_dependencies(op.outputs):
gradient_op = _internal_py_func(
func=eagerly_executed_grad,
inp=dy,
Tout=[tensor.dtype for tensor in op.inputs],
use_eager_py_func=True,
is_grad_func=True)
if not context.executing_eagerly():
# In graph mode, we find the func object from its token and
# notify the eager func object it needs to support the gradients.
func = _py_funcs.get(token.decode())
assert isinstance(func, EagerFunc), (
f"EagerPyFuncGrad called on a non-EagerFunc object: {func}.")
func.set_support_graph_mode_gradient()
return gradient_op
@tf_export("py_function")
@dispatch.add_dispatch_support
def eager_py_func(func, inp, Tout, name=None):
"""Wraps a python function into a TensorFlow op that executes it eagerly.
This function allows expressing computations in a TensorFlow graph as
Python functions. In particular, it wraps a Python function `func`
in a once-differentiable TensorFlow operation that executes it with eager
execution enabled. As a consequence, `tf.py_function` makes it
possible to express control flow using Python constructs (`if`, `while`,
`for`, etc.), instead of TensorFlow control flow constructs (`tf.cond`,
`tf.while_loop`). For example, you might use `tf.py_function` to
implement the log huber function:
```python
def log_huber(x, m):
if tf.abs(x) <= m:
return x**2
else:
return m**2 * (1 - 2 * tf.math.log(m) + tf.math.log(x**2))
x = tf.constant(1.0)
m = tf.constant(2.0)
with tf.GradientTape() as t:
t.watch([x, m])
y = tf.py_function(func=log_huber, inp=[x, m], Tout=tf.float32)
dy_dx = t.gradient(y, x)
assert dy_dx.numpy() == 2.0
```
You can also use `tf.py_function` to debug your models at runtime
using Python tools, i.e., you can isolate portions of your code that
you want to debug, wrap them in Python functions and insert `pdb` tracepoints
or print statements as desired, and wrap those functions in
`tf.py_function`.
For more information on eager execution, see the
[Eager guide](https://tensorflow.org/guide/eager).
`tf.py_function` is similar in spirit to `tf.compat.v1.py_func`, but unlike
the latter, the former lets you use TensorFlow operations in the wrapped
Python function. In particular, while `tf.compat.v1.py_func` only runs on CPUs
and wraps functions that take NumPy arrays as inputs and return NumPy arrays
as outputs, `tf.py_function` can be placed on GPUs and wraps functions
that take Tensors as inputs, execute TensorFlow operations in their bodies,
and return Tensors as outputs.
Note: We recommend to avoid using `tf.py_function` outside of prototyping
and experimentation due to the following known limitations:
* Calling `tf.py_function` will acquire the Python Global Interpreter Lock
(GIL) that allows only one thread to run at any point in time. This will
preclude efficient parallelization and distribution of the execution of the
program.
* The body of the function (i.e. `func`) will not be serialized in a
`GraphDef`. Therefore, you should not use this function if you need to
serialize your model and restore it in a different environment.
* The operation must run in the same address space as the Python program
that calls `tf.py_function()`. If you are using distributed
TensorFlow, you must run a `tf.distribute.Server` in the same process as the
program that calls `tf.py_function()` and you must pin the created
operation to a device in that server (e.g. using `with tf.device():`).
* Currently `tf.py_function` is not compatible with XLA. Calling
`tf.py_function` inside `tf.function(jit_comiple=True)` will raise an
error.
Args:
func: A Python function that accepts `inp` as arguments, and returns a
value (or list of values) whose type is described by `Tout`.
inp: Input arguments for `func`. A list whose elements are `Tensor`s or
`CompositeTensors` (such as `tf.RaggedTensor`); or a single `Tensor` or
`CompositeTensor`.
Tout: The type(s) of the value(s) returned by `func`. One of the
following.
* If `func` returns a `Tensor` (or a value that can be converted to a
Tensor): the `tf.DType` for that value.
* If `func` returns a `CompositeTensor`: The `tf.TypeSpec` for that value.
* If `func` returns `None`: the empty list (`[]`).
* If `func` returns a list of `Tensor` and `CompositeTensor` values:
a corresponding list of `tf.DType`s and `tf.TypeSpec`s for each value.
name: A name for the operation (optional).
Returns:
The value(s) computed by `func`: a `Tensor`, `CompositeTensor`, or list of
`Tensor` and `CompositeTensor`; or an empty list if `func` returns `None`.
"""
if ops.executing_eagerly_outside_functions():
with ops.device(context.context().host_address_space()):
return _internal_py_func(
func=func, inp=inp, Tout=Tout, use_eager_py_func=True, name=name)
return _internal_py_func(
func=func, inp=inp, Tout=Tout, use_eager_py_func=True, name=name)
def py_func_common(func, inp, Tout, stateful=True, name=None):
"""Wraps a python function and uses it as a TensorFlow op.
Given a python function `func`, which takes numpy arrays as its
arguments and returns numpy arrays as its outputs, wrap this function as an
operation in a TensorFlow graph. The following snippet constructs a simple
TensorFlow graph that invokes the `np.sinh()` NumPy function as a operation
in the graph:
```python
def my_func(x):
# x will be a numpy array with the contents of the placeholder below
return np.sinh(x)
input = tf.compat.v1.placeholder(tf.float32)
y = tf.compat.v1.py_func(my_func, [input], tf.float32)
```
**N.B.** The `tf.compat.v1.py_func()` operation has the following known
limitations:
* The body of the function (i.e. `func`) will not be serialized in a
`GraphDef`. Therefore, you should not use this function if you need to
serialize your model and restore it in a different environment.
* The operation must run in the same address space as the Python program
that calls `tf.compat.v1.py_func()`. If you are using distributed
TensorFlow, you
must run a `tf.distribute.Server` in the same process as the program that
calls
`tf.compat.v1.py_func()` and you must pin the created operation to a device
in that
server (e.g. using `with tf.device():`).
Note: It produces tensors of unknown shape and rank as shape inference
does not work on arbitrary Python code.
If you need the shape, you need to set it based on statically
available information.
E.g.
```python
import tensorflow as tf
import numpy as np
def make_synthetic_data(i):
return np.cast[np.uint8](i) * np.ones([20,256,256,3],
dtype=np.float32) / 10.
def preprocess_fn(i):
ones = tf.py_function(make_synthetic_data,[i],tf.float32)
ones.set_shape(tf.TensorShape([None, None, None, None]))
ones = tf.image.resize(ones, [224,224])
return ones
ds = tf.data.Dataset.range(10)
ds = ds.map(preprocess_fn)
```
Args:
func: A Python function, which accepts `ndarray` objects as arguments and
returns a list of `ndarray` objects (or a single `ndarray`). This function
must accept as many arguments as there are tensors in `inp`, and these
argument types will match the corresponding `tf.Tensor` objects in `inp`.
The returns `ndarray`s must match the number and types defined `Tout`.
Important Note: Input and output numpy `ndarray`s of `func` are not
guaranteed to be copies. In some cases their underlying memory will be
shared with the corresponding TensorFlow tensors. In-place modification
or storing `func` input or return values in python datastructures
without explicit (np.)copy can have non-deterministic consequences.
inp: A list of `Tensor` objects.
Tout: A list or tuple of tensorflow data types or a single tensorflow data
type if there is only one, indicating what `func` returns.
stateful: (Boolean.) If True, the function should be considered stateful. If
a function is stateless, when given the same input it will return the same
output and have no observable side effects. Optimizations such as common
subexpression elimination are only performed on stateless operations.
name: A name for the operation (optional).
Returns:
A list of `Tensor` or a single `Tensor` which `func` computes.
@compatibility(TF2)
This name was deprecated and removed in TF2, but `tf.numpy_function` is a
near-exact replacement, just drop the `stateful` argument (all
`tf.numpy_function` calls are considered stateful). It is compatible with
eager execution and `tf.function`.
`tf.py_function` is a close but not an exact replacement, passing TensorFlow
tensors to the wrapped function instead of NumPy arrays, which provides
gradients and can take advantage of accelerators.
Before:
>>> def fn_using_numpy(x):
... x[0] = 0.
... return x
>>> tf.compat.v1.py_func(fn_using_numpy, inp=[tf.constant([1., 2.])],
... Tout=tf.float32, stateful=False)
<tf.Tensor: shape=(2,), dtype=float32, numpy=array([0., 2.], dtype=float32)>
After:
>>> tf.numpy_function(fn_using_numpy, inp=[tf.constant([1., 2.])],
... Tout=tf.float32)
<tf.Tensor: shape=(2,), dtype=float32, numpy=array([0., 2.], dtype=float32)>
@end_compatibility
"""
if context.executing_eagerly():
result = func(*[np.array(x) for x in inp])
result = nest.flatten(result)
result = [x if x is None else ops.convert_to_tensor(x) for x in result]
if len(result) == 1:
# Mimic the automatic unwrapping in graph-mode py_func
result, = result
return result
if ops.executing_eagerly_outside_functions():
with ops.device(context.context().host_address_space()):
return _internal_py_func(
func=func,
inp=inp,
Tout=Tout,
stateful=stateful,
use_eager_py_func=False,
name=name)
return _internal_py_func(
func=func,
inp=inp,
Tout=Tout,
stateful=stateful,
use_eager_py_func=False,
name=name)
@deprecation.deprecated(
date=None,
instructions="""tf.py_func is deprecated in TF V2. Instead, there are two
options available in V2.
- tf.py_function takes a python function which manipulates tf eager
tensors instead of numpy arrays. It's easy to convert a tf eager tensor to
an ndarray (just call tensor.numpy()) but having access to eager tensors
means `tf.py_function`s can use accelerators such as GPUs as well as
being differentiable using a gradient tape.
- tf.numpy_function maintains the semantics of the deprecated tf.py_func
(it is not differentiable, and manipulates numpy arrays). It drops the
stateful argument making all functions stateful.
""")
@tf_export(v1=["py_func"])
@dispatch.add_dispatch_support
def py_func(func, inp, Tout, stateful=True, name=None):
return py_func_common(func, inp, Tout, stateful, name=name)
py_func.__doc__ = "%s" % py_func_common.__doc__
[文档]@tf_export("numpy_function")
@dispatch.add_dispatch_support
def numpy_function(func, inp, Tout, stateful=True, name=None):
"""Wraps a python function and uses it as a TensorFlow op.
Given a python function `func` wrap this function as an operation in a
TensorFlow function. `func` must take numpy arrays as its arguments and
return numpy arrays as its outputs.
The following example creates a TensorFlow graph with `np.sinh()` as an
operation in the graph:
>>> def my_numpy_func(x):
... # x will be a numpy array with the contents of the input to the
... # tf.function
... return np.sinh(x)
>>> @tf.function(input_signature=[tf.TensorSpec(None, tf.float32)])
... def tf_function(input):
... y = tf.numpy_function(my_numpy_func, [input], tf.float32)
... return y * y
>>> tf_function(tf.constant(1.))
<tf.Tensor: shape=(), dtype=float32, numpy=1.3810978>
Comparison to `tf.py_function`:
`tf.py_function` and `tf.numpy_function` are very similar, except that
`tf.numpy_function` takes numpy arrays, and not `tf.Tensor`s. If you want the
function to contain `tf.Tensors`, and have any TensorFlow operations executed
in the function be differentiable, please use `tf.py_function`.
Note: We recommend to avoid using `tf.numpy_function` outside of
prototyping and experimentation due to the following known limitations:
* Calling `tf.numpy_function` will acquire the Python Global Interpreter Lock
(GIL) that allows only one thread to run at any point in time. This will
preclude efficient parallelization and distribution of the execution of the
program. Therefore, you are discouraged to use `tf.numpy_function` outside
of prototyping and experimentation.
* The body of the function (i.e. `func`) will not be serialized in a
`tf.SavedModel`. Therefore, you should not use this function if you need to
serialize your model and restore it in a different environment.
* The operation must run in the same address space as the Python program
that calls `tf.numpy_function()`. If you are using distributed
TensorFlow, you must run a `tf.distribute.Server` in the same process as the
program that calls `tf.numpy_function` you must pin the created
operation to a device in that server (e.g. using `with tf.device():`).
* Currently `tf.numpy_function` is not compatible with XLA. Calling
`tf.numpy_function` inside `tf.function(jit_comiple=True)` will raise an
error.
* Since the function takes numpy arrays, you cannot take gradients
through a numpy_function. If you require something that is differentiable,
please consider using tf.py_function.
Args:
func: A Python function, which accepts `numpy.ndarray` objects as arguments
and returns a list of `numpy.ndarray` objects (or a single
`numpy.ndarray`). This function must accept as many arguments as there are
tensors in `inp`, and these argument types will match the corresponding
`tf.Tensor` objects in `inp`. The returns `numpy.ndarray`s must match the
number and types defined `Tout`.
Important Note: Input and output `numpy.ndarray`s of `func` are not
guaranteed to be copies. In some cases their underlying memory will be
shared with the corresponding TensorFlow tensors. In-place modification
or storing `func` input or return values in python datastructures
without explicit (np.)copy can have non-deterministic consequences.
inp: A list of `tf.Tensor` objects.
Tout: A list or tuple of tensorflow data types or a single tensorflow data
type if there is only one, indicating what `func` returns.
stateful: (Boolean.) Setting this argument to False tells the runtime to
treat the function as stateless, which enables certain optimizations.
A function is stateless when given the same input it will return the
same output and have no side effects; its only purpose is to have a
return value.
The behavior for a stateful function with the `stateful` argument False
is undefined. In particular, caution should be taken when
mutating the input arguments as this is a stateful operation.
name: (Optional) A name for the operation.
Returns:
Single or list of `tf.Tensor` which `func` computes.
"""
return py_func_common(func, inp, Tout, stateful=stateful, name=name)
def _as_dtype_or_type_spec(t):
return t if isinstance(t, type_spec.TypeSpec) else dtypes.as_dtype(t)
def _wrap_for_composites(func, inp, Tout):
"""Wraps user inputs to support composite tensors for `py_function`.
1. Flattens `inp` to a list of Tensors (by flattening any composite tensors).
2. Creates a wrapper fuction for `func` that expects flat inputs and:
- Packs the inputs into the input structure expected by `func`.
- Calls `func` with the packed inputs.
- Checks that `func`'s output matches `Tout`.
- Flattens func`'s output to a list of Tensors (flattening any composite
tensors).
Args:
func: The function to wrap (`func` argument to `py_function`).
inp: The input arguments for func (`inp` argument to `py_function`).
Tout: The expected output types for func (`Tout` argument to `py_function).
Returns:
A tuple `(func, inp, Tout, out_structure)`, where `func` is the wrapped
function, `inp` is the flattened inputs, `Tout` is the list of expected
dtypes for the flattened outputs, and `out_structure` is the expected
output structure (which can be used to pack the output tensors).
"""
in_structure = [
v if isinstance(v, composite_tensor.CompositeTensor) else 1 for v in inp
]
inp = nest.flatten_up_to(in_structure, inp, expand_composites=True)
out_structure = Tout
Tout = [
v.dtype if isinstance(v, tensor_spec.TensorSpec) else v
for v in nest.flatten(Tout, expand_composites=True)
]
def wrapped_func(*flat_inp):
structured_inp = nest.pack_sequence_as(
in_structure, flat_inp, expand_composites=True)
out = func(*structured_inp)
if not out_structure:
return [] # Ignore return value if none is requested/expected.
if not isinstance(out, (list, tuple)):
out = [out] # func may return a single value instead of a list.
flat_out = []
for elt, expected_type in zip(out, out_structure):
if (isinstance(expected_type, type_spec.TypeSpec) and
not isinstance(expected_type, tensor_spec.TensorSpec)):
if not expected_type.is_compatible_with(elt):
# pylint: disable=protected-access
raise ValueError(
f"py_function: func={func} returned {out!r}, "
f"which did not match Tout={out_structure!r}.\nIn particular, "
f"{elt!r} is not compatible with {expected_type!r}.")
flat_out.extend(nest.flatten(elt, expand_composites=True))
else:
# Pro-actively check if the return value is a composite tensor when
# we expect a Tensor. We would catch this later (when we call
# convert_to_tensor), but checking it here lets us give a better
# error message.
if isinstance(elt, composite_tensor.CompositeTensor):
raise ValueError(
f"py_function: func={func} returned {out!r}, "
f"which did not match Tout={out_structure!r}.\nIn particular, "
f"{elt!r} is not a Tensor.")
flat_out.append(elt)
return flat_out
return wrapped_func, inp, Tout, out_structure
ops.NotDifferentiable("PyFunc")
ops.NotDifferentiable("PyFuncStateless")