为什么pytorch loss越来越高？答案

【问题标题】：why pytorch loss grow higher and higher?为什么pytorch loss越来越高？
【发布时间】：2021-08-28 09:01:07
【问题描述】：

我使用nn.BCEWithLogitsLoss()
当我训练我的模型时，损失越来越大，为什么？我该如何解决这个问题？

基本代码：

loss_fn = nn.BCEWithLogitsLoss()

def train_loop(dataloader, model, loss_fn, optimizer):
    for batch, (X, y) in enumerate(dataloader):
        #X,y=X.to(device), y.to(device)
        m = nn.Sigmoid()
        predict=model(X.float())
        loss=loss_fn(m(predict),y.unsqueeze(1).float())

        optimizer.zero_grad()
        loss.backward()# Calculate Gradients
        optimizer.step()# Update Weights

完整代码：

import pandas as pd
import numpy as np
import torch
from torch.utils.data import Dataset
from torch.utils.data import DataLoader
import torch.nn as nn

class myDataset(Dataset):
    def __init__(self,data,label):#, annotations_file, img_dir, transform=None, target_transform=None):
        df = pd.read_csv(data, encoding='gbk')
        df = df.fillna(value=0)
        self.data = np.array(df)

        df = pd.read_csv(label, encoding='gbk')
        df = df.fillna(value=0)
        self.label = np.array(df).reshape(-1)

        #self.transform = transform
        #self.target_transform = target_transform

    def __len__(self):
        return len(self.data)

    def __getitem__(self, idx):
        return self.data[idx], self.label[idx]

class Network(nn.Module):
    def __init__(self):
        super(Network, self).__init__()
        self.flatten = nn.Flatten()
        self.network = nn.Sequential(
            #nn.Conv2d(in_channels=1, out_channels=6,kernel_size=5),
            nn.Linear(27, 100),
            nn.ReLU(),
            nn.Linear(100, 512),
            nn.ReLU(),
            nn.Linear(512, 512),
            nn.ReLU(),
            nn.Linear(512, 1),
            nn.ReLU()
        )
    def forward(self, x):
        x=self.flatten(x)
        return self.network(x)

def train_loop(dataloader, model, loss_fn, optimizer):
    for batch, (X, y) in enumerate(dataloader):
        #X,y=X.to(device), y.to(device)
        m = nn.Sigmoid()
        predict=model(X.float())
        loss=loss_fn(m(predict),y.unsqueeze(1).float())

        optimizer.zero_grad()
        loss.backward()# Calculate Gradients
        optimizer.step()# Update Weights

        if batch % 100 == 0:
            loss, current = loss.item(), batch * len(X)
            print(f"loss: {loss:>7f}  [{current:>5d}/{len(dataloader.dataset):>5d}]")

model=Network()
batch_size = 64
learning_rate = 1e-3
epochs = 5
loss_fn = nn.BCEWithLogitsLoss()
optimizer = torch.optim.Adam(model.parameters(), lr=learning_rate)

trainDataloader = DataLoader(myDataset("mydata/traindata.csv","mydata/trainlabel.csv"),batch_size=batch_size,shuffle=True)
train_loop(trainDataloader, model, loss_fn, optimizer)

【问题讨论】：

标签： python pytorch loss-function

【解决方案1】：

我认为你不需要这条线m = nn.Sigmoid()。

文档上说：This loss combines a Sigmoid layer and the BCELoss in one single class.你可以查一下损失here。

def train_loop(dataloader, model, loss_fn, optimizer):
    for batch, (X, y) in enumerate(dataloader):
        #X,y=X.to(device), y.to(device)
        predict=model(X.float())
        loss=loss_fn(predict,y.unsqueeze(1).float())

【讨论】：