# coding=utf-8

# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
#
# This source code is licensed under the BSD license found in the
# LICENSE file in the root directory of this source tree.

# Copyright (c) 2020, NVIDIA CORPORATION.  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 os
import random

import numpy
import torch
import torch.distributed as dist
import torch.multiprocessing as mp

from fairscale.nn.model_parallel.random import model_parallel_cuda_manual_seed


class IdentityLayer(torch.nn.Module):
    def __init__(self, size, scale=1.0):
        super(IdentityLayer, self).__init__()
        self.weight = torch.nn.Parameter(scale * torch.randn(size))

    def forward(self):
        return self.weight


def set_random_seed(seed):
    """Set random seed for reproducability."""
    random.seed(seed)
    numpy.random.seed(seed)
    torch.manual_seed(seed)
    model_parallel_cuda_manual_seed(seed)


def dist_init(rank, world_size):
    os.environ["MASTER_ADDR"] = "localhost"
    os.environ["MASTER_PORT"] = "29501"
    dist.init_process_group(backend="nccl", rank=rank, world_size=world_size)
    torch.cuda.set_device(rank)


def get_world_sizes():
    limit = torch.cuda.device_count()
    return [x for x in [1, 2, 4, 8] if x <= limit]


def spawn_for_all_world_sizes(test_func, world_sizes=get_world_sizes()):
    for world_size in world_sizes:
        mp.spawn(test_func, args=(world_size,), nprocs=world_size, join=True)