'jit.save/load' support save/load function without parameters.

[hbwx24]

PR types

Function optimization

PR changes

APIs

Describe

paddle.jit.save/load支持保存function，只保存了program，没有保存参数。因此没有.pdparam和.info文件。
示例如下：

import paddle
from paddle.static import InputSpec


def example1():
    @paddle.jit.to_static
    def fun(inputs):
        return paddle.tanh(inputs)

    path = 'test_jit_save_load_function_1/func'
    inps = paddle.rand([3, 6])
    origin = fun(inps)

    paddle.jit.save(fun, path)
    load_func = paddle.jit.load(path)

    load_result = load_func(inps)
    print((load_result - origin).abs().max() < 1e-10)


def example2():
    @paddle.jit.to_static(input_spec=[
        InputSpec(shape=[None, 6], dtype='float32', name='x'),
    ])
    def fun(inputs):
        return paddle.nn.functional.relu(inputs)

    path = 'test_jit_save_load_function_2/func'
    inps = paddle.rand([3, 6])
    origin = fun(inps)

    paddle.jit.save(fun, path)
    load_func = paddle.jit.load(path)
    load_result = load_func(inps)
    print((load_result - origin).abs().max() < 1e-10)


def example3():
    def fun(inputs):
        return paddle.tanh(inputs)

    path = 'test_jit_save_load_function_3/func'
    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)
    print((load_result - origin).abs().max() < 1e-10)


example1()
example2()
example3()

以下情况是不支持的：

def fun(inputs):
    l=paddle.nn.Linear(2, 3)
    y=l(inputs)
    return paddle.nn.functional.relu(y)

文档：红框内为本次修改的内容
http://10.136.157.23:8090/documentation/docs/en/api/paddle/fluid/dygraph/jit/save_en.html

[paddle-bot-old]

Thanks for your contribution!
Please wait for the result of CI firstly. See Paddle CI Manual for details.

[chenwhql]

这里我们要支持的是不是function，而不是StaticFunction，当时输入是普通function的时候，像layer一样根据input_spec对其进行转换，现在这样写，会导致存function的情况下，input_spec这个参数就没什么意义了吧

[hbwx24]

Done， thx.

[chenwhql]

还有两点问题：

1. 这个改动，文档也需要配合修改一下，参数类型和描述要涵盖function
2. 之前实现的时候可能条件卡得比较严，对于layer来讲，如果layer没有参数，是不是也不需要存pdparams和pdparams.info

[hbwx24]

还有两点问题：

1. 这个改动，文档也需要配合修改一下，参数类型和描述要涵盖function
2. 之前实现的时候可能条件卡得比较严，对于layer来讲，如果layer没有参数，是不是也不需要存pdparams和pdparams.info

Done,thx.

[zhhsplendid]

Since function cannot save parameters, you should give a Note or Warning and had better explain the reason for users.

[hbwx24]

Done, thx.

[zhhsplendid]

When not isinstance(layer, Layer), that means it is a function, should we also save function's name to model_filename and params_filename ?

[zhhsplendid]

LGTM

[TCChenlong]

LGTM

[TCChenlong]

LGTM