1

我正在尝试训练 Deeplab Resnet V3 对自定义数据集执行语义分割。我一直在本地机器上工作，但我的 GPU 只是一个小型 Quadro T1000，所以我决定将我的模型转移到 Google Colab 上，以利用他们的 GPU 实例并获得更好的结果。

虽然我得到了我希望的速度提升，但与我的本地机器相比，我在 colab 上的训练损失大不相同。我复制并粘贴了完全相同的代码，所以我能找到的唯一区别在于数据集中。我使用的是完全相同的数据集，除了 colab 上的数据集是 Google Drive 上本地数据集的副本。我注意到驱动器订单文件在 Windows 上有所不同，但我看不出这是一个问题，因为我随机打乱了数据集。我知道这些随机分裂可能会导致输出的微小差异，但是训练损失的大约 10 倍的差异是没有意义的。

我还尝试使用不同的随机种子、不同的批量大小、不同的 train_test_split 参数以及将优化器从 SGD 更改为 Adam 在 colab 上运行该版本，但是，这仍然会导致模型很早就收敛，损失约为 0.5。

这是我的代码：

import torch
from torch.utils import data
from torchvision import transforms
from customdatasets import SegmentationDataSet
import pathlib
from sklearn.model_selection import train_test_split
from customtransforms import Compose, AlbuSeg2d, DenseTarget
from customtransforms import MoveAxis, Normalize01, Resize
import albumentations
import matplotlib.pyplot as plt
import time
import GPUtil



def get_filenames_of_path(path: pathlib.Path, ext: str = '*'):
    """Returns a list of files in a directory/path. Uses pathlib."""
    filenames = [file for file in path.glob(ext) if file.is_file()]
    return filenames


if __name__ == '__main__':

    root = pathlib.Path.cwd() / 'train'
    inputs = get_filenames_of_path(root / 'input')
    targets = get_filenames_of_path(root / 'target')

    

# training transformations and augmentations
    transforms_training = Compose([
        Resize(input_size=(128, 128, 3), target_size=(128, 128)),
        AlbuSeg2d(albu=albumentations.HorizontalFlip(p=0.5)),
        MoveAxis(),
        Normalize01()
    ])
# validation transformations
    transforms_validation = Compose([
        Resize(input_size=(128, 128, 3), target_size=(128, 128)),
        MoveAxis(),
        Normalize01()
    ])
    if torch.cuda.is_available():
        device = torch.device('cuda')
    else:
        device = torch.device('cpu')

    random_seed = 142
    train_size = 0.8

    inputs_train, inputs_valid = train_test_split(
        inputs,
        random_state=random_seed,
        train_size=train_size,
        shuffle=True)
    targets_train, targets_valid = train_test_split(
        targets,
        random_state=random_seed,
        train_size=train_size,
        shuffle=True)

    dataset_train = SegmentationDataSet(inputs=inputs_train,
                                    targets=targets_train,
                                    transform=transforms_training,
                                    device=device)

    dataset_valid = SegmentationDataSet(inputs=inputs_valid,
                                    targets=targets_valid,
                                    transform=transforms_validation,
                                    device=device)


    dataloader_training = data.DataLoader(dataset=dataset_train,
                                      batch_size=15,
                                      shuffle=True,
                                      num_workers=4,
                                      pin_memory=True)

    dataloader_validation = data.DataLoader(dataset=dataset_valid,
                                        batch_size=15,
                                        shuffle=True,
                                        num_workers=4,
                                        pin_memory=True)


    model = torch.hub.load('pytorch/vision:v0.6.0', 'deeplabv3_resnet101', pretrained=False)


    criterion = torch.nn.CrossEntropyLoss()

    model = model.to(device)

    optimizer = torch.optim.SGD(model.parameters(), lr=0.001, momentum=0.99)


    epochs = 10
    steps = 0
    running_loss = 0
    print_every = 10
    train_losses, valid_losses = [], []

    start_time = time.time()
    prev_time = time.time()


    for epoch in range(epochs):
        #Training
        for inputs, labels in dataloader_training:
            steps += 1
            inputs, labels = inputs.to(device, non_blocking=True), labels.to(device,non_blocking=True)
            optimizer.zero_grad()
            logps = model(inputs)
            loss = criterion(logps['out'], labels)
            loss.backward()
            optimizer.step()
            running_loss += loss.item()

            if steps % print_every == 0:
                train_losses.append(running_loss / len(dataloader_training))
                epoch_time = time.time()
                elasped_time = epoch_time - prev_time
                prev_time = epoch_time
                print(f"Epoch {epoch + 1}/{epochs}.. "
                    f"Train loss: {running_loss / print_every:.3f}.. "
                    f"Elapsed time: {elasped_time}")

                running_loss = 0
                model.train()
        # Evaluation
        valid_loss = 0
        accuracy = 0
        model.eval()
        with torch.no_grad():
            for inputs, labels in dataloader_validation:
                inputs, labels = inputs.to(device, non_blocking=True), labels.to(device, non_blocking=True)
                logps = model.forward(inputs)
                batch_loss = criterion(logps['out'], labels)
                valid_loss += batch_loss.item()

                ps = torch.exp(logps['out'])
                top_p, top_class = ps.topk(1, dim=1)
                equals = top_class == labels.view(*top_class.shape)
                accuracy += torch.mean(equals.type(torch.FloatTensor)).item()
        valid_losses.append(valid_loss / len(dataloader_validation))
        print(f"Epoch {epoch + 1}/{epochs}.. "
            f"Validation loss: {valid_loss / len(dataloader_training):.3f}.. "
            f"Validation accuracy: {accuracy / len(dataloader_training):.3f} ")
        model.train()
    torch.save(model, 'model.pth')

    end_time = time.time()
    total_time = end_time - start_time
    print("Total Time: ", total_time)
    plt.plot(train_losses, label='Training loss')
    plt.plot(valid_losses, label='Validation loss')
    plt.legend(frameon=False)
    plt.show()

这是 Colab 上一个 epoch 的输出：

Epoch 1/10.. Train loss: 2.080.. Elapsed time: 12.156640768051147
Epoch 1/10.. Train loss: 1.231.. Elapsed time: 8.76858925819397
Epoch 1/10.. Train loss: 1.051.. Elapsed time: 8.315532445907593
Epoch 1/10.. Train loss: 0.890.. Elapsed time: 8.249168634414673
Epoch 1/10.. Train loss: 0.839.. Elapsed time: 8.248667478561401
Epoch 1/10.. Train loss: 0.807.. Elapsed time: 8.120820999145508
Epoch 1/10.. Train loss: 0.742.. Elapsed time: 8.298616886138916
Epoch 1/10.. Train loss: 0.726.. Elapsed time: 8.170734167098999
Epoch 1/10.. Train loss: 0.677.. Elapsed time: 8.221246004104614
Epoch 1/10.. Train loss: 0.698.. Elapsed time: 8.124614000320435
Epoch 1/10.. Train loss: 0.675.. Elapsed time: 8.197462558746338
Epoch 1/10.. Train loss: 0.682.. Elapsed time: 8.263437509536743
Epoch 1/10.. Train loss: 0.626.. Elapsed time: 8.156179189682007
Epoch 1/10.. Train loss: 0.632.. Elapsed time: 8.268096446990967
Epoch 1/10.. Train loss: 0.616.. Elapsed time: 8.214547872543335
Epoch 1/10.. Train loss: 0.585.. Elapsed time: 8.31475019454956
Epoch 1/10.. Train loss: 0.598.. Elapsed time: 8.388074398040771
Epoch 1/10.. Train loss: 0.626.. Elapsed time: 8.179292440414429
Epoch 1/10.. Train loss: 0.612.. Elapsed time: 8.252359390258789
Epoch 1/10.. Train loss: 0.592.. Elapsed time: 8.284745693206787
Epoch 1/10.. Train loss: 0.597.. Elapsed time: 8.31213927268982
Epoch 1/10.. Train loss: 0.566.. Elapsed time: 8.164374113082886
Epoch 1/10.. Train loss: 0.556.. Elapsed time: 8.300082206726074
Epoch 1/10.. Train loss: 0.568.. Elapsed time: 8.26304841041565
Epoch 1/10.. Train loss: 0.572.. Elapsed time: 8.309881448745728
Epoch 1/10.. Train loss: 0.586.. Elapsed time: 8.211671352386475
Epoch 1/10.. Train loss: 0.586.. Elapsed time: 8.321797609329224
Epoch 1/10.. Train loss: 0.535.. Elapsed time: 8.318871021270752
Epoch 1/10.. Train loss: 0.543.. Elapsed time: 8.152915239334106
Epoch 1/10.. Train loss: 0.569.. Elapsed time: 8.251380205154419
Epoch 1/10.. Train loss: 0.526.. Elapsed time: 8.29153847694397
Epoch 1/10.. Train loss: 0.565.. Elapsed time: 8.15071702003479
Epoch 1/10.. Train loss: 0.542.. Elapsed time: 8.253364562988281
Epoch 1/10.. Validation loss: 0.182.. Validation accuracy: 0.271

这是我本地机器上的输出：

Epoch 1/10.. Train loss: 2.932.. Elapsed time: 32.148621797561646
Epoch 1/10.. Train loss: 1.852.. Elapsed time: 14.120505809783936
Epoch 1/10.. Train loss: 0.887.. Elapsed time: 14.210048198699951
Epoch 1/10.. Train loss: 0.618.. Elapsed time: 14.23294186592102
Epoch 1/10.. Train loss: 0.549.. Elapsed time: 14.212541103363037
Epoch 1/10.. Train loss: 0.519.. Elapsed time: 14.047481775283813
Epoch 1/10.. Train loss: 0.506.. Elapsed time: 14.060708045959473
Epoch 1/10.. Train loss: 0.347.. Elapsed time: 14.301624059677124
Epoch 1/10.. Train loss: 0.399.. Elapsed time: 13.9844491481781
Epoch 1/10.. Train loss: 0.361.. Elapsed time: 13.957871913909912
Epoch 1/10.. Train loss: 0.305.. Elapsed time: 14.164010763168335
Epoch 1/10.. Train loss: 0.296.. Elapsed time: 14.001536846160889
Epoch 1/10.. Train loss: 0.298.. Elapsed time: 14.019971132278442
Epoch 1/10.. Train loss: 0.271.. Elapsed time: 13.951345443725586
Epoch 1/10.. Train loss: 0.252.. Elapsed time: 14.037938594818115
Epoch 1/10.. Train loss: 0.283.. Elapsed time: 13.944657564163208
Epoch 1/10.. Train loss: 0.299.. Elapsed time: 13.977224826812744
Epoch 1/10.. Train loss: 0.219.. Elapsed time: 13.941975355148315
Epoch 1/10.. Train loss: 0.242.. Elapsed time: 13.936140060424805
Epoch 1/10.. Train loss: 0.244.. Elapsed time: 13.942122459411621
Epoch 1/10.. Train loss: 0.216.. Elapsed time: 13.960899114608765
Epoch 1/10.. Train loss: 0.186.. Elapsed time: 13.956881523132324
Epoch 1/10.. Train loss: 0.241.. Elapsed time: 13.944581985473633
Epoch 1/10.. Train loss: 0.203.. Elapsed time: 13.934357404708862
Epoch 1/10.. Train loss: 0.189.. Elapsed time: 13.938358306884766
Epoch 1/10.. Train loss: 0.181.. Elapsed time: 13.944468021392822
Epoch 1/10.. Train loss: 0.186.. Elapsed time: 13.946297407150269
Epoch 1/10.. Train loss: 0.164.. Elapsed time: 13.940366744995117
Epoch 1/10.. Train loss: 0.165.. Elapsed time: 13.938241720199585
Epoch 1/10.. Train loss: 0.176.. Elapsed time: 14.015569925308228
Epoch 1/10.. Train loss: 0.165.. Elapsed time: 14.019208669662476
Epoch 1/10.. Train loss: 0.175.. Elapsed time: 14.149503469467163
Epoch 1/10.. Train loss: 0.159.. Elapsed time: 14.128302097320557
Epoch 1/10.. Train loss: 0.155.. Elapsed time: 13.935027837753296
Epoch 1/10.. Train loss: 0.137.. Elapsed time: 13.937382221221924
Epoch 1/10.. Train loss: 0.127.. Elapsed time: 13.929635524749756
Epoch 1/10.. Train loss: 0.133.. Elapsed time: 13.935472011566162
Epoch 1/10.. Train loss: 0.152.. Elapsed time: 13.922808647155762
Epoch 1/10.. Validation loss: 0.032.. Validation accuracy: 0.239

我不会粘贴更多，因为它很长并且需要一段时间才能运行，但是到第三个 epoch 结束时，Colab 模型的损失仍然在 0.5 左右反弹，而在本地它达到 0.02。

如果有人可以帮助我解决这个问题，将不胜感激。

4

1 回答 1

0

我通过将训练数据解压缩到 Google Drive 并从那里读取文件而不是使用 Colab 命令将文件夹直接解压缩到我的工作区来解决了这个问题。我完全不知道为什么会导致问题；对图像及其对应的张量进行快速目视检查看起来不错，但我无法通过大约 6,000 张图像中的每一张来检查每一张。如果有人知道为什么这会导致问题，请告诉我！

于 2021-03-09T09:24:20.647 回答