test_clip_grad.py

# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
#
# Copyright (c) 2014-2021 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 platform
import weakref

import numpy as np
import pytest

import megengine as mge
import megengine.autodiff as ad
import megengine.functional as F
import megengine.module as M
import megengine.optimizer as optim


class Net(M.Module):
    def __init__(self):
        super().__init__()
        self.conv1 = M.Conv2d(3, 64, kernel_size=7, stride=2, padding=3, bias=False)
        self.bn1 = M.BatchNorm2d(64)
        self.avgpool = M.AvgPool2d(kernel_size=5, stride=5, padding=0)
        self.fc = M.Linear(64, 10)

    def forward(self, x):
        x = self.conv1(x)
        x = self.bn1(x)
        x = F.relu(x)
        x = self.avgpool(x)
        x = F.avg_pool2d(x, 22)
        x = F.flatten(x, 1)
        x = self.fc(x)
        return x


def save_grad_value(net):
    for param in net.parameters():
        param.grad_backup = param.grad.numpy().copy()


def test_clip_grad_norm():
    net = Net()
    x = mge.tensor(np.random.randn(10, 3, 224, 224))
    gm = ad.GradManager().attach(net.parameters())
    opt = optim.SGD(net.parameters(), 1e-3, momentum=0.9)
    with gm:
        loss = net(x).sum()
        gm.backward(loss)
    save_grad_value(net)
    max_norm = 1.0
    original_norm = optim.clip_grad_norm(net.parameters(), max_norm=max_norm, ord=2)
    scale = max_norm / original_norm
    for param in net.parameters():
        np.testing.assert_almost_equal(param.grad.numpy(), param.grad_backup * scale)
    opt.step().clear_grad()


def test_clip_grad_value():
    net = Net()
    x = np.random.randn(10, 3, 224, 224).astype("float32")
    gm = ad.GradManager().attach(net.parameters())
    opt = optim.SGD(net.parameters(), 1e-3, momentum=0.9)
    with gm:
        y = net(x)
        y = y.mean()
        gm.backward(y)
    save_grad_value(net)
    max_val = 5
    min_val = -2
    optim.clip_grad_value(net.parameters(), lower=min_val, upper=max_val)
    for param in net.parameters():
        np.testing.assert_almost_equal(
            param.grad.numpy(),
            np.maximum(np.minimum(param.grad_backup, max_val), min_val),
        )
    opt.step().clear_grad()