# -*- coding: utf-8 -*-
# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
#
# Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
import numpy as np
import pytest

import megengine
import megengine.optimizer as optimizer
from megengine import Parameter, tensor
from megengine.module import BatchNorm2d


def test_frozen_bn():
    nchannel = 3
    m = BatchNorm2d(nchannel, freeze=True)

    saved_var = m.running_var.numpy()
    saved_mean = m.running_mean.numpy()
    saved_wt = m.weight.numpy()
    saved_bias = m.bias.numpy()

    optim = optimizer.SGD(m.parameters(), lr=1.0)
    optim.zero_grad()

    data = np.random.random((6, nchannel, 2, 2)).astype("float32")
    with optim.record():
        loss = m(data).mean()
        optim.backward(loss)
    optim.step()

    np.testing.assert_equal(m.running_var.numpy(), saved_var)
    np.testing.assert_equal(m.running_mean.numpy(), saved_mean)
    np.testing.assert_equal(m.weight.numpy(), saved_wt)
    np.testing.assert_equal(m.bias.numpy(), saved_bias)
    np.testing.assert_almost_equal(loss.numpy(), data.mean(), 5)


def test_bn_no_track_stat():
    nchannel = 3
    m = BatchNorm2d(nchannel, track_running_stats=False)

    optim = optimizer.SGD(m.parameters(), lr=1.0)
    optim.zero_grad()

    data = np.random.random((6, nchannel, 2, 2)).astype("float32")
    with optim.record():
        loss = m(data).sum()
        optim.backward(loss)
    optim.step()


def test_bn_no_track_stat2():
    nchannel = 3
    m = BatchNorm2d(nchannel)  # Init with track_running_stat = True
    m.track_running_stats = False

    # m.running_var and m.running_mean created during init time
    saved_var = m.running_var.numpy()
    assert saved_var is not None
    saved_mean = m.running_mean.numpy()
    assert saved_mean is not None

    optim = optimizer.SGD(m.parameters(), lr=1.0)
    optim.zero_grad()

    data = np.random.random((6, nchannel, 2, 2)).astype("float32")
    with optim.record():
        loss = m(data).sum()
        optim.backward(loss)
    optim.step()

    np.testing.assert_equal(m.running_var.numpy(), saved_var)
    np.testing.assert_equal(m.running_mean.numpy(), saved_mean)


def test_bn_no_track_stat3():
    nchannel = 3
    m = BatchNorm2d(nchannel, track_running_stats=False)
    m.track_running_stats = True
    data = np.random.random((6, nchannel, 2, 2)).astype("float32")
    with pytest.raises(Exception):
        m(data)