PyReader
- class
paddle.fluid.io.
PyReader
(feed_list=None, capacity=None, use_double_buffer=True, iterable=True, return_list=False)[源代码]
在python中为数据输入创建一个reader对象。将使用python线程预取数据,并将其异步插入队列。当调用Executor.run(…)时,将自动提取队列中的数据。
- 参数:
- feed_list (list(Variable)|tuple(Variable)) - feed变量列表,由
fluid.layers.data()
创建。 - capacity (int) - PyReader对象内部维护队列的容量大小。单位是batch数量。若reader读取速度较快,建议设置较大的capacity值。
- use_double_buffer (bool) - 是否使用
double_buffer_reader
。若use_double_buffer=True,PyReader会异步地预读取下一个batch的数据,可加速数据读取过程,但同时会占用少量的CPU/GPU存储,即一个batch输入数据的存储空间。 - iterable (bool) - 所创建的DataLoader对象是否可迭代。
- return_list (bool) - 每个设备上的数据是否以list形式返回。仅在iterable = True模式下有效。若return_list = False,每个设备上的返回数据均是str -> LoDTensor的映射表,其中映射表的key是每个输入变量的名称。若return_list = True,则每个设备上的返回数据均是list(LoDTensor)。推荐在静态图模式下使用return_list = False,在动态图模式下使用return_list = True。
- feed_list (list(Variable)|tuple(Variable)) - feed变量列表,由
返回: 被创建的reader对象
返回类型: reader (Reader)
代码示例
1.如果iterable=False,则创建的PyReader对象几乎与 fluid.layers.py_reader()
相同。算子将被插入program中。用户应该在每个epoch之前调用 start()
,并在epoch结束时捕获 Executor.run()
抛出的 fluid.core.EOFException
。一旦捕获到异常,用户应该调用 reset()
手动重置reader。
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 5
- BATCH_SIZE = 3
- def network(image, label):
- # 用户定义网络,此处以softmax回归为例
- predict = fluid.layers.fc(input=image, size=10, act='softmax')
- return fluid.layers.cross_entropy(input=predict, label=label)
- def reader_creator_random_image_and_label(height, width):
- def reader():
- for i in range(ITER_NUM):
- fake_image = np.random.uniform(low=0,
- high=255,
- size=[height, width])
- fake_label = np.ones([1])
- yield fake_image, fake_label
- return reader
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- label = fluid.layers.data(name='label', shape=[1], dtype='int64')
- reader = fluid.io.PyReader(feed_list=[image, label],
- capacity=4,
- iterable=False)
- user_defined_reader = reader_creator_random_image_and_label(784, 784)
- reader.decorate_sample_list_generator(
- paddle.batch(user_defined_reader, batch_size=BATCH_SIZE))
- loss = network(image, label)
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for i in range(EPOCH_NUM):
- reader.start()
- while True:
- try:
- executor.run(feed=None)
- except fluid.core.EOFException:
- reader.reset()
- break
2.如果iterable=True,则创建的PyReader对象与程序分离。程序中不会插入任何算子。在本例中,创建的reader是一个python生成器,它是可迭代的。用户应将从PyReader对象生成的数据输入 Executor.run(feed=…)
。
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 5
- BATCH_SIZE = 10
- def network(image, label):
- # 用户定义网络,此处以softmax回归为例
- predict = fluid.layers.fc(input=image, size=10, act='softmax')
- return fluid.layers.cross_entropy(input=predict, label=label)
- def reader_creator_random_image(height, width):
- def reader():
- for i in range(ITER_NUM):
- fake_image = np.random.uniform(low=0, high=255, size=[height, width]),
- fake_label = np.ones([1])
- yield fake_image, fake_label
- return reader
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- label = fluid.layers.data(name='label', shape=[1], dtype='int64')
- reader = fluid.io.PyReader(feed_list=[image, label], capacity=4, iterable=True, return_list=False)
- user_defined_reader = reader_creator_random_image(784, 784)
- reader.decorate_sample_list_generator(
- paddle.batch(user_defined_reader, batch_size=BATCH_SIZE),
- fluid.core.CPUPlace())
- loss = network(image, label)
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for _ in range(EPOCH_NUM):
- for data in reader():
- executor.run(feed=data, fetch_list=[loss])
- return_list=True,返回值将用list表示而非dict,通常用于动态图模式中。
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 5
- BATCH_SIZE = 10
- def reader_creator_random_image(height, width):
- def reader():
- for i in range(ITER_NUM):
- yield np.random.uniform(low=0, high=255, size=[height, width]), \
- np.random.random_integers(low=0, high=9, size=[1])
- return reader
- place = fluid.CPUPlace()
- with fluid.dygraph.guard(place):
- py_reader = fluid.io.PyReader(capacity=2, return_list=True)
- user_defined_reader = reader_creator_random_image(784, 784)
- py_reader.decorate_sample_list_generator(
- paddle.batch(user_defined_reader, batch_size=BATCH_SIZE),
- place)
- for image, label in py_reader():
- relu = fluid.layers.relu(image)
start
()
启动数据输入线程。只能在reader对象不可迭代时调用。
代码示例
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- BATCH_SIZE = 10
- def generator():
- for i in range(5):
- yield np.random.uniform(low=0, high=255, size=[784, 784]),
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- reader = fluid.io.PyReader(feed_list=[image], capacity=4, iterable=False)
- reader.decorate_sample_list_generator(
- paddle.batch(generator, batch_size=BATCH_SIZE))
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for i in range(3):
- reader.start()
- while True:
- try:
- executor.run(feed=None)
- except fluid.core.EOFException:
- reader.reset()
- break
reset
()
当 fluid.core.EOFException
抛出时重置reader对象。只能在reader对象不可迭代时调用。
代码示例
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- BATCH_SIZE = 10
- def generator():
- for i in range(5):
- yield np.random.uniform(low=0, high=255, size=[784, 784]),
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- reader = fluid.io.PyReader(feed_list=[image], capacity=4, iterable=False)
- reader.decorate_sample_list_generator(
- paddle.batch(generator, batch_size=BATCH_SIZE))
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for i in range(3):
- reader.start()
- while True:
- try:
- executor.run(feed=None)
- except fluid.core.EOFException:
- reader.reset()
- break
decorate_sample_generator
(sample_generator, batch_size, drop_last=True, places=None)
设置PyReader对象的数据源。
提供的 sample_generator
应该是一个python生成器,它生成的数据类型应为list(numpy.ndarray)。
当PyReader对象可迭代时,必须设置 places
。
如果所有的输入都没有LOD,这个方法比 decorate_sample_list_generator(paddle.batch(sample_generator, …))
更快。
- 参数:
- sample_generator (generator) – Python生成器,yield 类型为list(numpy.ndarray)
- batch_size (int) – batch size,必须大于0
- drop_last (bool) – 当样本数小于batch数量时,是否删除最后一个batch
- places (None|list(CUDAPlace)|list(CPUPlace)) – 位置列表。当PyReader可迭代时必须被提供
代码示例
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 15
- BATCH_SIZE = 3
- def network(image, label):
- # 用户定义网络,此处以softmax回归为例
- predict = fluid.layers.fc(input=image, size=10, act='softmax')
- return fluid.layers.cross_entropy(input=predict, label=label)
- def random_image_and_label_generator(height, width):
- def generator():
- for i in range(ITER_NUM):
- fake_image = np.random.uniform(low=0,
- high=255,
- size=[height, width])
- fake_label = np.array([1])
- yield fake_image, fake_label
- return generator
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- label = fluid.layers.data(name='label', shape=[1], dtype='int64')
- reader = fluid.io.PyReader(feed_list=[image, label], capacity=4, iterable=True)
- user_defined_generator = random_image_and_label_generator(784, 784)
- reader.decorate_sample_generator(user_defined_generator,
- batch_size=BATCH_SIZE,
- places=[fluid.CPUPlace()])
- loss = network(image, label)
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for _ in range(EPOCH_NUM):
- for data in reader():
- executor.run(feed=data, fetch_list=[loss])
decorate_sample_list_generator
(reader, places=None)
设置PyReader对象的数据源。
提供的 reader
应该是一个python生成器,它生成列表(numpy.ndarray)类型的批处理数据。
当PyReader对象不可迭代时,必须设置 places
。
- 参数:
- reader (generator) – 返回列表(numpy.ndarray)类型的批处理数据的Python生成器
- places (None|list(CUDAPlace)|list(CPUPlace)) – 位置列表。当PyReader可迭代时必须被提供
代码示例
- import paddle
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 15
- BATCH_SIZE = 3
- def network(image, label):
- # 用户定义网络,此处以softmax回归为例
- predict = fluid.layers.fc(input=image, size=10, act='softmax')
- return fluid.layers.cross_entropy(input=predict, label=label)
- def random_image_and_label_generator(height, width):
- def generator():
- for i in range(ITER_NUM):
- fake_image = np.random.uniform(low=0,
- high=255,
- size=[height, width])
- fake_label = np.ones([1])
- yield fake_image, fake_label
- return generator
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- label = fluid.layers.data(name='label', shape=[1], dtype='int64')
- reader = fluid.io.PyReader(feed_list=[image, label], capacity=4, iterable=True)
- user_defined_generator = random_image_and_label_generator(784, 784)
- reader.decorate_sample_list_generator(
- paddle.batch(user_defined_generator, batch_size=BATCH_SIZE),
- fluid.core.CPUPlace())
- loss = network(image, label)
- executor = fluid.Executor(fluid.core.CPUPlace())
- executor.run(fluid.default_startup_program())
- for _ in range(EPOCH_NUM):
- for data in reader():
- executor.run(feed=data, fetch_list=[loss])
decorate_batch_generator
(reader, places=None)
设置PyReader对象的数据源。
提供的 reader
应该是一个python生成器,它生成列表(numpy.ndarray)类型或LoDTensor类型的批处理数据。
当PyReader对象不可迭代时,必须设置 places
。
- 参数:
- reader (generator) – 返回LoDTensor类型的批处理数据的Python生成器
- places (None|list(CUDAPlace)|list(CPUPlace)) – 位置列表。当PyReader可迭代时必须被提供
代码示例
- import paddle.fluid as fluid
- import numpy as np
- EPOCH_NUM = 3
- ITER_NUM = 15
- BATCH_SIZE = 3
- def network(image, label):
- # 用户定义网络,此处以softmax回归为例
- predict = fluid.layers.fc(input=image, size=10, act='softmax')
- return fluid.layers.cross_entropy(input=predict, label=label)
- def random_image_and_label_generator(height, width):
- def generator():
- for i in range(ITER_NUM):
- batch_image = np.random.uniform(low=0,
- high=255,
- size=[BATCH_SIZE, height, width])
- batch_label = np.ones([BATCH_SIZE, 1])
- batch_image = batch_image.astype('float32')
- batch_label = batch_label.astype('int64')
- yield batch_image, batch_label
- return generator
- image = fluid.layers.data(name='image', shape=[784, 784], dtype='float32')
- label = fluid.layers.data(name='label', shape=[1], dtype='int64')
- reader = fluid.io.PyReader(feed_list=[image, label], capacity=4, iterable=True)
- user_defined_generator = random_image_and_label_generator(784, 784)
- reader.decorate_batch_generator(user_defined_generator, fluid.CPUPlace())
- loss = network(image, label)
- executor = fluid.Executor(fluid.CPUPlace())
- executor.run(fluid.default_startup_program())
- for _ in range(EPOCH_NUM):
- for data in reader():
- executor.run(feed=data, fetch_list=[loss])
next
()
获取下一个数据。用户不应直接调用此方法。此方法用于PaddlePaddle框架内部实现Python 2.x的迭代器协议。