create_py_reader_by_data

paddle.fluid.layers. create_py_reader_by_data ( capacity, feed_list, name=None, use_double_buffer=True ) [源代码]

创建一个Python端提供数据的reader。该OP与 py_reader 类似,不同点在于它能够从feed变量列表读取数据。

参数

  • capacity (int) - py_reader 维护的队列缓冲区的容量大小。单位是batch数量。若reader读取速度较快,建议设置较大的 capacity 值。

  • feed_list (list(Variable)) - feed变量列表,这些变量一般由 fluid.data() 创建。

  • name (str,可选) - 具体用法请参见 Name,一般无需设置,默认值为 None。

  • use_double_buffer (bool,可选) - 是否使用双缓冲区,双缓冲区是为了预读下一个batch的数据、异步CPU -> GPU拷贝。默认值为True。

返回

能够从feed变量列表读取数据的reader,数据类型和feed变量列表中变量的数据类型相同。

返回类型

reader

代码示例

import paddle
import paddle.fluid as fluid
import paddle.dataset.mnist as mnist

def network(img, label):
    # User defined network. Here a simple regression as example
    predict = fluid.layers.fc(input=img, size=10, act='softmax')
    loss = fluid.layers.cross_entropy(input=predict, label=label)
    return fluid.layers.mean(loss)

MEMORY_OPT = False
USE_CUDA = False

image = fluid.data(name='image', shape=[None, 1, 28, 28], dtype='float32')
label = fluid.data(name='label', shape=[None, 1], dtype='int64')
reader = fluid.layers.create_py_reader_by_data(capacity=64,
                                               feed_list=[image, label])
reader.decorate_paddle_reader(
    paddle.reader.shuffle(paddle.batch(mnist.train(), batch_size=5), buf_size=500))
img, label = fluid.layers.read_file(reader)
loss = network(img, label) # The definition of custom network and the loss function

place = fluid.CUDAPlace(0) if USE_CUDA else fluid.CPUPlace()
exe = fluid.Executor(place)
exe.run(fluid.default_startup_program())

build_strategy = fluid.BuildStrategy()
build_strategy.memory_optimize = True if MEMORY_OPT else False
exec_strategy = fluid.ExecutionStrategy()
compiled_prog = fluid.compiler.CompiledProgram(
fluid.default_main_program()).with_data_parallel(
    loss_name=loss.name,
    build_strategy=build_strategy,
    exec_strategy=exec_strategy)

for epoch_id in range(2):
reader.start()
try:
    while True:
        exe.run(compiled_prog, fetch_list=[loss.name])
except fluid.core.EOFException:
    reader.reset()