模型保存常见问题-使用文档-PaddlePaddle深度学习平台
飞桨框架2.1对模型与参数的保存与载入相关接口进行了梳理:对于训练调优场景,我们推荐使用paddle.save/load保存和载入模型;对于推理部署场景,我们推荐使用paddle.jit.save/load(动态图)和paddle.static.save/load_inference_model(静态图)保存载入模型。
飞桨保存载入相关接口包括:
paddle.static.save_inference_model
paddle.static.load_inference_model
各接口关系如下图所示:


paddle.Model.fit (训练接口,同时带有参数保存的功能)
paddle.Model.save
paddle.Model.load
飞桨框架2.0高阶API仅有一套Save/Load接口,表意直观,体系清晰,若有需要,建议直接阅读相关API文档,此处不再赘述。
本教程着重介绍飞桨框架2.1的各个保存载入接口的关系及各种使用场景,不对接口参数进行详细介绍,如果需要了解具体接口参数的含义,请直接阅读对应API文档。
若仅需要保存/载入模型的参数,可以使用 paddle.save/load 结合Layer和Optimizer的state_dict达成目的,此处state_dict是对象的持久参数的载体,dict的key为参数名,value为参数真实的numpy array值。
结合以下简单示例,介绍参数保存和载入的方法,以下示例完成了一个简单网络的训练过程:
- import numpy as np
- import paddle
- import paddle.nn as nn
- import paddle.optimizer as opt
-
- BATCH_SIZE = 16
- BATCH_NUM = 4
- EPOCH_NUM = 4
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- # define a random dataset
- class RandomDataset(paddle.io.Dataset):
- def __init__(self, num_samples):
- self.num_samples = num_samples
-
- def __getitem__(self, idx):
- image = np.random.random([IMAGE_SIZE]).astype('float32')
- label = np.random.randint(0, CLASS_NUM - 1, (1, )).astype('int64')
- return image, label
-
- def __len__(self):
- return self.num_samples
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- def forward(self, x):
- return self._linear(x)
-
- def train(layer, loader, loss_fn, opt):
- for epoch_id in range(EPOCH_NUM):
- for batch_id, (image, label) in enumerate(loader()):
- out = layer(image)
- loss = loss_fn(out, label)
- loss.backward()
- opt.step()
- opt.clear_grad()
- print("Epoch {} batch {}: loss = {}".format(
- epoch_id, batch_id, np.mean(loss.numpy())))
-
- # create network
- layer = LinearNet()
- loss_fn = nn.CrossEntropyLoss()
- adam = opt.Adam(learning_rate=0.001, parameters=layer.parameters())
-
- # create data loader
- dataset = RandomDataset(BATCH_NUM * BATCH_SIZE)
- loader = paddle.io.DataLoader(dataset,
- batch_size=BATCH_SIZE,
- shuffle=True,
- drop_last=True,
- num_workers=2)
-
- # train
- train(layer, loader, loss_fn, adam)
参数保存时,先获取目标对象(Layer或者Optimzier)的state_dict,然后将state_dict保存至磁盘,示例如下(接前述示例):
- # save
- paddle.save(layer.state_dict(), "linear_net.pdparams")
- paddle.save(adam.state_dict(), "adam.pdopt")
参数载入时,先从磁盘载入保存的state_dict,然后通过set_state_dict方法配置到目标对象中,示例如下(接前述示例):
- # load
- layer_state_dict = paddle.load("linear_net.pdparams")
- opt_state_dict = paddle.load("adam.pdopt")
-
- layer.set_state_dict(layer_state_dict)
- adam.set_state_dict(opt_state_dict)
若仅需要保存/载入模型的参数,可以使用 paddle.save/load 结合Program的state_dict达成目的,此处state_dict与动态图state_dict概念类似,dict的key为参数名,value为参数真实的值。若想保存整个模型,需要使用``paddle.save``将Program和state_dict都保存下来。
结合以下简单示例,介绍参数保存和载入的方法:
- import paddle
- import paddle.static as static
-
- paddle.enable_static()
-
- # create network
- x = paddle.static.data(name="x", shape=[None, 224], dtype='float32')
- z = paddle.static.nn.fc(x, 10)
-
- place = paddle.CPUPlace()
- exe = paddle.static.Executor(place)
- exe.run(paddle.static.default_startup_program())
- prog = paddle.static.default_main_program()
参数保存时,先获取Program的state_dict,然后将state_dict保存至磁盘,示例如下(接前述示例):
paddle.save(prog.state_dict(), "temp/model.pdparams")
如果想要保存整个静态图模型,除了state_dict还需要保存Program
paddle.save(prog, "temp/model.pdmodel")
如果只保存了state_dict,可以跳过此段代码,直接载入state_dict。如果模型文件中包含Program和state_dict,请先载入Program,示例如下(接前述示例):
prog = paddle.load("temp/model.pdmodel")
参数载入时,先从磁盘载入保存的state_dict,然后通过set_state_dict方法配置到Program中,示例如下(接前述示例):
- state_dict = paddle.load("temp/model.pdparams")
- prog.set_state_dict(state_dict)
若要同时保存/载入动态图模型结构和参数,可以使用 paddle.jit.save/load 实现。
模型&参数存储根据训练模式不同,有两种使用情况:
动转静训练 + 模型&参数保存
动态图训练 + 模型&参数保存
3.1.1.1 动转静训练 + 模型&参数保存¶
动转静训练相比直接使用动态图训练具有更好的执行性能,训练完成后,直接将目标Layer传入 paddle.jit.save 保存即可。:
一个简单的网络训练示例如下:
- import numpy as np
- import paddle
- import paddle.nn as nn
- import paddle.optimizer as opt
-
- BATCH_SIZE = 16
- BATCH_NUM = 4
- EPOCH_NUM = 4
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- # define a random dataset
- class RandomDataset(paddle.io.Dataset):
- def __init__(self, num_samples):
- self.num_samples = num_samples
-
- def __getitem__(self, idx):
- image = np.random.random([IMAGE_SIZE]).astype('float32')
- label = np.random.randint(0, CLASS_NUM - 1, (1, )).astype('int64')
- return image, label
-
- def __len__(self):
- return self.num_samples
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static
- def forward(self, x):
- return self._linear(x)
-
- def train(layer, loader, loss_fn, opt):
- for epoch_id in range(EPOCH_NUM):
- for batch_id, (image, label) in enumerate(loader()):
- out = layer(image)
- loss = loss_fn(out, label)
- loss.backward()
- opt.step()
- opt.clear_grad()
- print("Epoch {} batch {}: loss = {}".format(
- epoch_id, batch_id, np.mean(loss.numpy())))
-
- # create network
- layer = LinearNet()
- loss_fn = nn.CrossEntropyLoss()
- adam = opt.Adam(learning_rate=0.001, parameters=layer.parameters())
-
- # create data loader
- dataset = RandomDataset(BATCH_NUM * BATCH_SIZE)
- loader = paddle.io.DataLoader(dataset,
- batch_size=BATCH_SIZE,
- shuffle=True,
- drop_last=True,
- num_workers=2)
-
- # train
- train(layer, loader, loss_fn, adam)
随后使用 paddle.jit.save 对模型和参数进行存储(接前述示例):
- # save
- path = "example.model/linear"
- paddle.jit.save(layer, path)
通过动转静训练后保存模型&参数,有以下三项注意点:
Layer对象的forward方法需要经由 paddle.jit.to_static 装饰
经过 paddle.jit.to_static 装饰forward方法后,相应Layer在执行时,会先生成描述模型的Program,然后通过执行Program获取计算结果,示例如下:
- import paddle
- import paddle.nn as nn
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static
- def forward(self, x):
- return self._linear(x)
若最终需要生成的描述模型的Program支持动态输入,可以同时指明模型的 InputSepc ,示例如下:
- import paddle
- import paddle.nn as nn
- from paddle.static import InputSpec
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static(input_spec=[InputSpec(shape=[None, 784], dtype='float32')])
- def forward(self, x):
- return self._linear(x)
2.请确保Layer.forward方法中仅实现预测功能,避免将训练所需的loss计算逻辑写入forward方法
Layer更准确的语义是描述一个具有预测功能的模型对象,接收输入的样本数据,输出预测的结果,而loss计算是仅属于模型训练中的概念。将loss计算的实现放到Layer.forward方法中,会使Layer在不同场景下概念有所差别,并且增大Layer使用的复杂性,这不是良好的编码行为,同时也会在最终保存预测模型时引入剪枝的复杂性,因此建议保持Layer实现的简洁性,下面通过两个示例对比说明
错误示例如下:
- import paddle
- import paddle.nn as nn
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static
- def forward(self, x, label=None):
- out = self._linear(x)
- if label:
- loss = nn.functional.cross_entropy(out, label)
- avg_loss = nn.functional.mean(loss)
- return out, avg_loss
- else:
- return out
正确示例如下:
- import paddle
- import paddle.nn as nn
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static
- def forward(self, x):
- return self._linear(x)
3.如果你需要保存多个方法,需要用 paddle.jit.to_static 装饰每一个需要被保存的方法。
只有在forward之外还需要保存其他方法时才用这个特性,如果仅装饰非forward的方法,而forward没有被装饰,是不符合规范的。此时 paddle.jit.save 的 input_spec 参数必须为None。
示例代码如下
- import paddle
- import paddle.nn as nn
- from paddle.static import InputSpec
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
- self._linear_2 = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static(input_spec=[InputSpec(shape=[None, IMAGE_SIZE], dtype='float32')])
- def forward(self, x):
- return self._linear(x)
-
- @paddle.jit.to_static(input_spec=[InputSpec(shape=[None, IMAGE_SIZE], dtype='float32')])
- def another_forward(self, x):
- return self._linear_2(x)
-
- inps = paddle.randn([1, IMAGE_SIZE])
- layer = LinearNet()
- before_0 = layer.another_forward(inps)
- before_1 = layer(inps)
- # save and load
- path = "example.model/linear"
- paddle.jit.save(layer, path)
保存的模型命名规则:forward的模型名字为:模型名+后缀,其他函数的模型名字为:模型名+函数名+后缀。每个函数有各自的pdmodel和pdiparams的文件,所有函数共用pdiparams.info。上述代码将在 example.model 文件夹下产生5个文件: linear.another_forward.pdiparams、 linear.pdiparams、 linear.pdmodel、 linear.another_forward.pdmodel、 linear.pdiparams.info
4.当使用 jit.save 保存函数时,jit.save 只保存这个函数对应的静态图 Program ,不会保存和这个函数相关的参数。如果你必须保存参数,请使用Layer封装这个函数。
示例代码如下:
- def fun(inputs):
- return paddle.tanh(inputs)
-
- path = 'func/model'
- inps = paddle.rand([3, 6])
- origin = fun(inps)
-
- paddle.jit.save(
- fun,
- path,
- input_spec=[
- InputSpec(
- shape=[None, 6], dtype='float32', name='x'),
- ])
- load_func = paddle.jit.load(path)
- load_result = load_func(inps)
3.1.1.2 动态图训练 + 模型&参数保存
动态图模式相比动转静模式更加便于调试,如果你仍需要使用动态图直接训练,也可以在动态图训练完成后调用 paddle.jit.save 直接保存模型和参数。
同样是一个简单的网络训练示例:
- import numpy as np
- import paddle
- import paddle.nn as nn
- import paddle.optimizer as opt
- from paddle.static import InputSpec
-
- BATCH_SIZE = 16
- BATCH_NUM = 4
- EPOCH_NUM = 4
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- # define a random dataset
- class RandomDataset(paddle.io.Dataset):
- def __init__(self, num_samples):
- self.num_samples = num_samples
-
- def __getitem__(self, idx):
- image = np.random.random([IMAGE_SIZE]).astype('float32')
- label = np.random.randint(0, CLASS_NUM - 1, (1, )).astype('int64')
- return image, label
-
- def __len__(self):
- return self.num_samples
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- def forward(self, x):
- return self._linear(x)
-
- def train(layer, loader, loss_fn, opt):
- for epoch_id in range(EPOCH_NUM):
- for batch_id, (image, label) in enumerate(loader()):
- out = layer(image)
- loss = loss_fn(out, label)
- loss.backward()
- opt.step()
- opt.clear_grad()
- print("Epoch {} batch {}: loss = {}".format(
- epoch_id, batch_id, np.mean(loss.numpy())))
-
- # create network
- layer = LinearNet()
- loss_fn = nn.CrossEntropyLoss()
- adam = opt.Adam(learning_rate=0.001, parameters=layer.parameters())
-
- # create data loader
- dataset = RandomDataset(BATCH_NUM * BATCH_SIZE)
- loader = paddle.io.DataLoader(dataset,
- batch_size=BATCH_SIZE,
- shuffle=True,
- drop_last=True,
- num_workers=2)
-
- # train
- train(layer, loader, loss_fn, adam)
训练完成后使用 paddle.jit.save 对模型和参数进行存储:
- # save
- path = "example.dy_model/linear"
- paddle.jit.save(
- layer=layer,
- path=path,
- input_spec=[InputSpec(shape=[None, 784], dtype='float32')])
动态图训练后使用 paddle.jit.save 保存模型和参数注意点如下:
相比动转静训练,Layer对象的forward方法不需要额外装饰,保持原实现即可
与动转静训练相同,请确保Layer.forward方法中仅实现预测功能,避免将训练所需的loss计算逻辑写入forward方法
在最后使用 paddle.jit.save 时,需要指定Layer的 InputSpec ,Layer对象forward方法的每一个参数均需要对应的 InputSpec 进行描述,不能省略。这里的 input_spec 参数支持两种类型的输入:
InputSpec 列表
使用InputSpec描述forward输入参数的shape,dtype和name,如前述示例(此处示例中name省略,name省略的情况下会使用forward的对应参数名作为name,所以这里的name为 x ):
- paddle.jit.save(
- layer=layer,
- path=path,
- input_spec=[InputSpec(shape=[None, 784], dtype='float32')])
Example Tensor 列表
除使用InputSpec之外,也可以直接使用forward训练时的示例输入,此处可以使用前述示例中迭代DataLoader得到的 image ,示例如下:
- paddle.jit.save(
- layer=layer,
- path=path,
- input_spec=[image])
载入模型参数,使用 paddle.jit.load 载入即可,载入后得到的是一个Layer的派生类对象 TranslatedLayer , TranslatedLayer 具有Layer具有的通用特征,支持切换 train 或者 eval 模式,可以进行模型调优或者预测。
为了规避变量名字冲突,载入之后会重命名变量。
载入模型及参数,示例如下:
- import numpy as np
- import paddle
- import paddle.nn as nn
- import paddle.optimizer as opt
-
- BATCH_SIZE = 16
- BATCH_NUM = 4
- EPOCH_NUM = 4
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- # load
- path = "example.model/linear"
- loaded_layer = paddle.jit.load(path)
载入模型及参数后进行预测,示例如下(接前述示例):
- # inference
- loaded_layer.eval()
- x = paddle.randn([1, IMAGE_SIZE], 'float32')
- pred = loaded_layer(x)
载入模型及参数后进行调优,示例如下(接前述示例):
- # define a random dataset
- class RandomDataset(paddle.io.Dataset):
- def __init__(self, num_samples):
- self.num_samples = num_samples
-
- def __getitem__(self, idx):
- image = np.random.random([IMAGE_SIZE]).astype('float32')
- label = np.random.randint(0, CLASS_NUM - 1, (1, )).astype('int64')
- return image, label
-
- def __len__(self):
- return self.num_samples
-
- def train(layer, loader, loss_fn, opt):
- for epoch_id in range(EPOCH_NUM):
- for batch_id, (image, label) in enumerate(loader()):
- out = layer(image)
- loss = loss_fn(out, label)
- loss.backward()
- opt.step()
- opt.clear_grad()
- print("Epoch {} batch {}: loss = {}".format(
- epoch_id, batch_id, np.mean(loss.numpy())))
-
- # fine-tune
- loaded_layer.train()
- dataset = RandomDataset(BATCH_NUM * BATCH_SIZE)
- loader = paddle.io.DataLoader(dataset,
- batch_size=BATCH_SIZE,
- shuffle=True,
- drop_last=True,
- num_workers=2)
- loss_fn = nn.CrossEntropyLoss()
- adam = opt.Adam(learning_rate=0.001, parameters=loaded_layer.parameters())
- train(loaded_layer, loader, loss_fn, adam)
- # save after fine-tuning
- paddle.jit.save(loaded_layer, "fine-tune.model/linear", input_spec=[x])
此外, paddle.jit.save 同时保存了模型和参数,如果你只需要从存储结果中载入模型的参数,可以使用 paddle.load 接口载入,返回所存储模型的state_dict,示例如下:
- import paddle
- import paddle.nn as nn
-
- IMAGE_SIZE = 784
- CLASS_NUM = 10
-
- class LinearNet(nn.Layer):
- def __init__(self):
- super(LinearNet, self).__init__()
- self._linear = nn.Linear(IMAGE_SIZE, CLASS_NUM)
-
- @paddle.jit.to_static
- def forward(self, x):
- return self._linear(x)
-
- # create network
- layer = LinearNet()
-
- # load
- path = "example.model/linear"
- state_dict = paddle.load(path)
-
- # inference
- layer.set_state_dict(state_dict, use_structured_name=False)
- layer.eval()
- x = paddle.randn([1, IMAGE_SIZE], 'float32')
- pred = layer(x)
保存/载入静态图推理模型,可以通过 paddle.static.save/load_inference_model 实现。示例如下:
- import paddle
- import numpy as np
-
- paddle.enable_static()
-
- # Build the model
- startup_prog = paddle.static.default_startup_program()
- main_prog = paddle.static.default_main_program()
- with paddle.static.program_guard(main_prog, startup_prog):
- image = paddle.static.data(name="img", shape=[64, 784])
- w = paddle.create_parameter(shape=[784, 200], dtype='float32')
- b = paddle.create_parameter(shape=[200], dtype='float32')
- hidden_w = paddle.matmul(x=image, y=w)
- hidden_b = paddle.add(hidden_w, b)
- exe = paddle.static.Executor(paddle.CPUPlace())
- exe.run(startup_prog)
静态图导出推理模型需要指定导出路径、输入、输出变量以及执行器。 save_inference_model 会裁剪Program的冗余部分,并导出两个文件: path_prefix.pdmodel 、 path_prefix.pdiparams 。示例如下(接前述示例):
- # Save the inference model
- path_prefix = "./infer_model"
- paddle.static.save_inference_model(path_prefix, [image], [hidden_b], exe)
载入静态图推理模型时,输入给 load_inference_model 的路径必须与 save_inference_model 的一致。示例如下(接前述示例):
- [inference_program, feed_target_names, fetch_targets] = (
- paddle.static.load_inference_model(path_prefix, exe))
- tensor_img = np.array(np.random.random((64, 784)), dtype=np.float32)
- results = exe.run(inference_program,
- feed={feed_target_names[0]: tensor_img},
- fetch_list=fetch_targets)
模型保存与载入-使用文档-PaddlePaddle深度学习平台