#   Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import print_function

import unittest
from functools import partial
import numpy as np
import paddle
import paddle.fluid as fluid
import contextlib


def get_places():
    places = [fluid.CPUPlace()]
    if fluid.core.is_compiled_with_cuda():
        places.append(fluid.CUDAPlace(0))
    return places


@contextlib.contextmanager
def prog_scope_guard(main_prog, startup_prog):
    scope = fluid.core.Scope()
    with fluid.unique_name.guard():
        with fluid.scope_guard(scope):
            with fluid.program_guard(main_prog, startup_prog):
                yield


def bow_net(data,
            label,
            dict_dim,
            is_sparse=False,
            emb_dim=128,
            hid_dim=128,
            hid_dim2=96,
            class_dim=2):
    """
    BOW net
    This model is from https://github.com/PaddlePaddle/models:
    fluid/PaddleNLP/text_classification/nets.py
    """
    emb = fluid.layers.embedding(
        input=data, is_sparse=is_sparse, size=[dict_dim, emb_dim])
    bow = fluid.layers.sequence_pool(input=emb, pool_type='sum')
    bow_tanh = fluid.layers.tanh(bow)
    fc_1 = fluid.layers.fc(input=bow_tanh, size=hid_dim, act="tanh")
    fc_2 = fluid.layers.fc(input=fc_1, size=hid_dim2, act="tanh")
    prediction = fluid.layers.fc(input=[fc_2], size=class_dim, act="softmax")
    cost = fluid.layers.cross_entropy(input=prediction, label=label)
    avg_cost = fluid.layers.mean(x=cost)

    return avg_cost


class TestWeightDecay(unittest.TestCase):
    def setUp(self):
        self.word_dict = paddle.dataset.imdb.word_dict()
        reader = paddle.batch(
            paddle.dataset.imdb.train(self.word_dict), batch_size=2)()
        self.train_data = [next(reader) for _ in range(5)]
        self.learning_rate = .5

    def run_program(self, place, feed_list):
        exe = fluid.Executor(place)
        feeder = fluid.DataFeeder(feed_list=feed_list, place=place)
        exe.run(fluid.default_startup_program())

        main_prog = fluid.default_main_program()
        param_list = [var.name for var in main_prog.block(0).all_parameters()]

        param_sum = []
        for data in self.train_data:
            out = exe.run(main_prog,
                          feed=feeder.feed(data),
                          fetch_list=param_list)
            p_sum = 0
            for v in out:
                p_sum += np.sum(np.abs(v))
            param_sum.append(p_sum)
        return param_sum

    def check_weight_decay(self, place, model):
        main_prog = fluid.framework.Program()
        startup_prog = fluid.framework.Program()
        startup_prog.random_seed = 1
        with prog_scope_guard(main_prog=main_prog, startup_prog=startup_prog):
            data = fluid.layers.data(
                name="words", shape=[1], dtype="int64", lod_level=1)
            label = fluid.layers.data(name="label", shape=[1], dtype="int64")
            avg_cost = model(data, label, len(self.word_dict))
            AdamW = fluid.contrib.extend_with_decoupled_weight_decay(
                fluid.optimizer.Adam)

            optimizer = AdamW(
                learning_rate=self.learning_rate,
                weight_decay=self.learning_rate)

            optimizer.minimize(avg_cost)
            param_sum = self.run_program(place, [data, label])

        return param_sum

    def check_weight_decay2(self, place, model):
        main_prog = fluid.framework.Program()
        startup_prog = fluid.framework.Program()
        startup_prog.random_seed = 1
        with prog_scope_guard(main_prog=main_prog, startup_prog=startup_prog):
            data = fluid.layers.data(
                name="words", shape=[1], dtype="int64", lod_level=1)
            label = fluid.layers.data(name="label", shape=[1], dtype="int64")

            avg_cost = model(data, label, len(self.word_dict))

            param_list = [(var, var * self.learning_rate)
                          for var in main_prog.block(0).all_parameters()]

            optimizer = fluid.optimizer.Adam(learning_rate=self.learning_rate)

            optimizer.minimize(avg_cost)
            for params in param_list:
                updated_p = fluid.layers.elementwise_sub(
                    x=params[0], y=params[1])
                fluid.layers.assign(input=updated_p, output=params[0])

            param_sum = self.run_program(place, [data, label])
        return param_sum

    def test_weight_decay(self):
        for place in get_places():
            model = partial(bow_net, is_sparse=False)
            param_sum1 = self.check_weight_decay(place, model)
            param_sum2 = self.check_weight_decay2(place, model)

            for i in range(len(param_sum1)):
                assert np.isclose(a=param_sum1[i], b=param_sum2[i], rtol=5e-5)


if __name__ == '__main__':
    unittest.main()