未验证 提交 455ed267 编写于 作者: G gfwm0502 提交者: GitHub

Modify English documents of while and while_loop (#23934)

test=develop test=document_fix
上级 7d4002e0
...@@ -854,12 +854,18 @@ class While(object): ...@@ -854,12 +854,18 @@ class While(object):
A new OP :ref:`api_fluid_layers_while_loop` is highly recommended instead of ``While`` if the shape of parameter ``cond`` is [1]. A new OP :ref:`api_fluid_layers_while_loop` is highly recommended instead of ``While`` if the shape of parameter ``cond`` is [1].
OP :ref:`api_fluid_layers_while_loop` is easier to use and is called with less code but does the same thing as ``While`` . OP :ref:`api_fluid_layers_while_loop` is easier to use and is called with less code but does the same thing as ``While`` .
Notice:
Local variables created in ``While`` are similar to that created in while of C++, and cannot be referenced externally.
As a result, they cannot be obtained through ``fetch_list`` of ``Executor``. If you would like to access the variable
out of ``while`` , PaddlePaddle provides ``assign`` API to assign local variables to external. Please refer to example
code 2 or refer to `issue#22724 <https://github.com/PaddlePaddle/Paddle/issues/22724>`_.
Args: Args:
cond(Variable): A Tensor whose data type is bool controlling whether to continue looping. cond(Variable): A Tensor whose data type is bool controlling whether to continue looping.
is_test(bool, optional): A flag indicating whether execution is in test phase. Default value is False. is_test(bool, optional): A flag indicating whether execution is in test phase. Default value is False.
name(str, optional): The default value is None. Normally there is no need for user to set this property. For more information, please refer to :ref:`api_guide_Name` . name(str, optional): The default value is None. Normally there is no need for user to set this property. For more information, please refer to :ref:`api_guide_Name` .
Examples: Examples 1:
.. code-block:: python .. code-block:: python
import paddle.fluid as fluid import paddle.fluid as fluid
...@@ -869,17 +875,45 @@ class While(object): ...@@ -869,17 +875,45 @@ class While(object):
loop_len = fluid.layers.fill_constant(shape=[1],dtype='int64', value=10) # loop length loop_len = fluid.layers.fill_constant(shape=[1],dtype='int64', value=10) # loop length
cond = fluid.layers.less_than(x=i, y=loop_len) cond = fluid.layers.less_than(x=i, y=loop_len)
while_op = fluid.layers.While(cond=cond) while_op = fluid.layers.While(cond=cond)
with while_op.block(): with while_op.block():
i = fluid.layers.increment(x=i, value=1, in_place=True) i = fluid.layers.increment(x=i, value=1, in_place=True)
fluid.layers.less_than(x=i, y=loop_len, cond=cond) fluid.layers.less_than(x=i, y=loop_len, cond=cond)
exe = fluid.Executor(fluid.CPUPlace()) exe = fluid.Executor(fluid.CPUPlace())
exe.run(fluid.default_startup_program()) exe.run(fluid.default_startup_program())
res = exe.run(fluid.default_main_program(), feed={}, fetch_list=[i]) res = exe.run(fluid.default_main_program(), feed={}, fetch_list=[i])
print(res) # [array([10])] print(res) # [array([10])]
Examples 2:
.. code-block:: python
import paddle.fluid as fluid
import numpy as np
i = fluid.layers.fill_constant(shape=[1], dtype='int64', value=0)
loop_len = fluid.layers.fill_constant(shape=[1], dtype='int64', value=10)
one = fluid.layers.fill_constant(shape=[1], dtype='float32', value=1)
data = fluid.data(name='data', shape=[1], dtype='float32')
sums = fluid.layers.fill_constant(shape=[1], dtype='float32', value=0) # Define the variable to be obtained ouside of While, which name should be different from the variable inside the While to be obtained
cond = fluid.layers.less_than(x=i, y=loop_len)
while_op = fluid.layers.While(cond=cond)
with while_op.block():
sums_tensor = fluid.layers.elementwise_add(x=data, y=data)
fluid.layers.assign(sums_tensor, sums) # Update the value of sums_tensor defined in While to the sums which defined outside of While through layers.assign
i = fluid.layers.increment(x=i, value=1, in_place=True)
data = fluid.layers.elementwise_add(x=data, y=one)
fluid.layers.less_than(x=i, y=loop_len, cond=cond)
feed_data = np.ones(1).astype('float32')
exe = fluid.Executor(fluid.CPUPlace())
exe.run(fluid.default_startup_program())
res = exe.run(fluid.default_main_program(), feed={'data': feed_data}, fetch_list=sums)
print(res[0]) # [2.] # Because the data in While does not update the value outside the While, the value of sums is [2.] after the loop
""" """
BEFORE_WHILE_BLOCK = 0 BEFORE_WHILE_BLOCK = 0
...@@ -946,6 +980,10 @@ def while_loop(cond, body, loop_vars, is_test=False, name=None): ...@@ -946,6 +980,10 @@ def while_loop(cond, body, loop_vars, is_test=False, name=None):
""" """
while_loop is one of the control flows. Repeats while_loop `body` until `cond` returns False. while_loop is one of the control flows. Repeats while_loop `body` until `cond` returns False.
Notice:
Local variables defined in ``body`` cannot be obtained through ``fetch_list`` of ``Executor`` , variables should
be defined outside ``body`` and placed in ``loop_vars`` for looping, then these variables can be fetched by ``fetch_list`` .
Args: Args:
cond(Callable): A callable returning a boolean tensor controlling whether to continue looping. And ``cond`` takes cond(Callable): A callable returning a boolean tensor controlling whether to continue looping. And ``cond`` takes
as many arguments as ``loop_vars`` . as many arguments as ``loop_vars`` .
...@@ -955,7 +993,7 @@ def while_loop(cond, body, loop_vars, is_test=False, name=None): ...@@ -955,7 +993,7 @@ def while_loop(cond, body, loop_vars, is_test=False, name=None):
is_test(bool, optional): A flag indicating whether execution is in test phase. Default value is False. is_test(bool, optional): A flag indicating whether execution is in test phase. Default value is False.
name(str, optional): Normally there is no need for users to set this property. For more information, please name(str, optional): Normally there is no need for users to set this property. For more information, please
refer to :ref:`api_guide_Name`. Default is None. refer to :ref:`api_guide_Name`. Default is None.
Returns: Returns:
A list or tuple of tensors or LoDTensorArrays which returned by ``body`` . A list or tuple of tensors or LoDTensorArrays which returned by ``body`` .
......
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