提交 bc46c527 编写于 作者: X Xin Pan

Add doc for while op

上级 0329ee74
......@@ -607,6 +607,60 @@ class WhileGuard(BlockGuard):
class While(object):
"""
while loop control flow.
Args:
cond (Variable): condition used to compare.
name (str): The name of this layer.
Examples:
.. code-block:: python
# The value these d0, d1 and d2 can be fed from python.
d0 = fluid.layers.data(
"d0", shape=[10], append_batch_size=False, dtype='float32')
d1 = fluid.layers.data(
"d1", shape=[10], append_batch_size=False, dtype='float32')
d2 = fluid.layers.data(
"d2", shape=[10], append_batch_size=False, dtype='float32')
i = fluid.layers.zeros(shape=[1], dtype='int64')
i.stop_gradient = True
init = fluid.layers.zeros(shape=[10], dtype='float32')
# Initialize mem_array from init
mem_array = fluid.layers.array_write(x=init, i=i)
# Initialize data_array from d0
data_array = fluid.layers.array_write(x=d0, i=i)
# Set a value to data_array using d1[i].
i = fluid.layers.increment(i)
fluid.layers.array_write(d1, i, array=data_array)
# Set a value to data_array using d2[i].
i = fluid.layers.increment(i)
fluid.layers.array_write(d2, i, array=data_array)
# Create a idx to start the while loop.
i = fluid.layers.zeros(shape=[1], dtype='int64')
i.stop_gradient = True
array_len = fluid.layers.fill_constant(
shape=[1], dtype='int64', value=3)
array_len.stop_gradient = True
# Create the while loop condition.
cond = fluid.layers.less_than(x=i, y=array_len)
# Within the loop, perform sums.
while_op = fluid.layers.While(cond=cond)
with while_op.block():
d = fluid.layers.array_read(array=data_array, i=i)
prev = fluid.layers.array_read(array=mem_array, i=i)
result = fluid.layers.sums(input=[d, prev])
i = fluid.layers.increment(x=i, in_place=True)
fluid.layers.array_write(result, i=i, array=mem_array)
fluid.layers.less_than(x=i, y=array_len, cond=cond)
sum_result = fluid.layers.array_read(array=mem_array, i=i)
"""
BEFORE_WHILE_BLOCK = 0
IN_WHILE_BLOCK = 1
AFTER_WHILE_BLOCK = 2
......
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