# -*- coding: UTF-8 -*-

# Copyright (c) 2022 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.

import numpy as np
import argparse
import ast
import time
import paddle
import paddle.fluid as fluid
from paddle.fluid.dygraph.nn import Linear
from paddle.distributed import fleet
from paddle.fluid.dygraph import nn
from paddle.fluid.framework import _test_eager_guard

from paddle.distributed.fleet.meta_parallel.sharding.group_sharded_stage3 import GroupShardedStage3
from paddle.distributed.fleet.meta_parallel.sharding.group_sharded_utils import GroupShardedScaler

epoch = 10
paddle.seed(2022)
np.random.seed(2022)
base_lr = 0.1
momentum_rate = 0.9
l2_decay = 1e-4


class MLP(fluid.Layer):

    def __init__(self, linear_size=1000, param_attr=None, bias_attr=None):
        super(MLP, self).__init__()

        self._linear1 = Linear(linear_size, linear_size)
        self._linear2 = Linear(linear_size, linear_size)
        self._linear3 = Linear(linear_size, 10)

    def forward(self, inputs):
        y = self._linear1(inputs)
        y = self._linear2(y)
        y = self._linear3(y)
        return y


def reader_decorator(linear_size=1000):

    def __reader__():
        for _ in range(100):
            img = np.random.rand(linear_size).astype('float32')
            label = np.ones(1).astype('int64')
            yield img, label

    return __reader__


def optimizer_setting(model, use_pure_fp16, opt_group=False):
    clip = paddle.nn.ClipGradByGlobalNorm(clip_norm=1.0)
    optimizer = paddle.optimizer.AdamW(parameters=[{
        "params": model.parameters()
    }] if opt_group else model.parameters(),
                                       learning_rate=0.001,
                                       weight_decay=0.00001,
                                       grad_clip=clip,
                                       multi_precision=use_pure_fp16)

    return optimizer


def train_mlp(model,
              use_pure_fp16=False,
              accumulate_grad=False,
              offload=False,
              batch_size=100,
              convert2cpu=False):
    group = paddle.distributed.new_group([0, 1])
    optimizer = optimizer_setting(model=model, use_pure_fp16=use_pure_fp16)

    if use_pure_fp16:
        model = paddle.amp.decorate(models=model,
                                    level='O2',
                                    save_dtype='float32')
        scaler = paddle.amp.GradScaler(init_loss_scaling=32768)
        scaler = GroupShardedScaler(scaler)

    model = GroupShardedStage3(model,
                               optimizer=optimizer,
                               group=group,
                               offload=offload,
                               segment_size=2**15)

    train_reader = paddle.batch(reader_decorator(),
                                batch_size=batch_size,
                                drop_last=True)

    train_loader = paddle.io.DataLoader.from_generator(capacity=32,
                                                       use_double_buffer=True,
                                                       iterable=True,
                                                       return_list=True,
                                                       use_multiprocess=True)
    train_loader.set_sample_list_generator(train_reader)

    for eop in range(epoch):
        model.train()
        for batch_id, data in enumerate(train_loader()):
            img, label = data
            label.stop_gradient = True
            img.stop_gradient = True
            with paddle.amp.auto_cast(True, level='O2'):
                out = model(img)
                loss = paddle.nn.functional.cross_entropy(input=out,
                                                          label=label)
            avg_loss = paddle.mean(x=loss.cast(dtype=paddle.float32))

            if accumulate_grad:
                avg_loss = avg_loss / 5

            if not use_pure_fp16:
                avg_loss.backward()
            else:
                scaler.scale(avg_loss).backward()

            if not accumulate_grad:
                if not use_pure_fp16:
                    optimizer.step()
                else:
                    scaler.step(optimizer)
                    scaler.update()
                optimizer.clear_grad()
        if accumulate_grad:
            if not use_pure_fp16:
                optimizer.step()
            else:
                scaler.step(optimizer)
                scaler.update()
            optimizer.clear_grad()
    if not convert2cpu:
        model.get_all_parameters()
    else:
        model.get_all_parameters(convert2cpu)
    return model.parameters()


def test_stage3_offload():
    paddle.distributed.init_parallel_env()
    mlp, mlp1, mlp2, mlp3, mlp4, mlp5, mlp6 = MLP(), MLP(), MLP(), MLP(), MLP(
    ), MLP(), MLP()
    state_dict = mlp.state_dict()
    mlp1.set_state_dict(state_dict)
    mlp2.set_state_dict(state_dict)
    mlp3.set_state_dict(state_dict)
    mlp4.set_state_dict(state_dict)
    mlp5.set_state_dict(state_dict)
    mlp6.set_state_dict(state_dict)

    # fp32 offload
    stage3_params = train_mlp(mlp1, use_pure_fp16=False)
    stage3_params_offload = train_mlp(mlp2, use_pure_fp16=False, offload=True)
    for i in range(len(stage3_params)):
        np.testing.assert_allclose(stage3_params[i].numpy(),
                                   stage3_params_offload[i].numpy(),
                                   rtol=1e-6,
                                   atol=1e-8)

    # fp16 offload
    stage3_params = train_mlp(mlp3, use_pure_fp16=True)
    stage3_params_offload = train_mlp(mlp4, use_pure_fp16=True, offload=True)
    for i in range(len(stage3_params)):
        np.testing.assert_allclose(stage3_params[i].numpy(),
                                   stage3_params_offload[i].numpy(),
                                   rtol=1e-2,
                                   atol=1e-2)

    # fp32 accumulate grad offload
    stage3_params = train_mlp(mlp5,
                              use_pure_fp16=False,
                              batch_size=20,
                              accumulate_grad=True)
    stage3_params_offload = train_mlp(mlp6,
                                      use_pure_fp16=False,
                                      accumulate_grad=True,
                                      offload=True,
                                      batch_size=20,
                                      convert2cpu=True)
    for i in range(len(stage3_params)):
        np.testing.assert_allclose(stage3_params[i].numpy(),
                                   stage3_params_offload[i].numpy(),
                                   rtol=1e-6,
                                   atol=1e-8)
    return


if __name__ == '__main__':
    with _test_eager_guard():
        test_stage3_offload()
