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Wraps a python function into a TensorFlow op that executes it eagerly.
tf.py_function(
func, inp, Tout, name=None
)
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:
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.
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.
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 aGraphDef
. 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 atf.distribute.Server
in the same process as the program that callstf.py_function()
and you must pin the created operation to a device in that server (e.g. usingwith tf.device():
).Currently
tf.py_function
is not compatible with XLA. Callingtf.py_function
insidetf.function(jit_compile=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.
|
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 .
|