解决RuntimeError: Trying to backward through the graph a second time

最新推荐文章于 2025-03-10 19:49:15 发布

AlbertTuring

最新推荐文章于 2025-03-10 19:49:15 发布

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分类专栏： debug 文章标签： pytorch

本文链接：https://blog.youkuaiyun.com/SCUTACM_L/article/details/144130086

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在写代码过程中遇到了RuntimeError: Trying to backward through the graph a second time 问题。我在网络上没有找到合适的解决方案，并且我的原始工程代码比较复杂，难以直接询问chatgpt。为了更方便debug，我写了一个简单的代码复现这个错误。

import torch
import torch.nn as nn
import torch.optim as optim

class A(nn.Module):
    def __init__(self):
        super(A, self).__init__()
        self.fc = nn.Linear(512, 512)
        self.v_image = nn.Parameter(torch.randn(1, 512))
        self.fuse_image = []
    def forward(self, x):
        out = self.fc(x)
        t = torch.matmul(out, self.v_image.T)
        self.fuse_image.append(t)
        return out, self.fuse_image

model = A()
criterion = nn.L1Loss()
optimizer = optim.Adam(model.parameters(), lr=0.01)
for i in range(50):
    optimizer.zero_grad()
    x = torch.randn(2, 512)
    out, fuse_image = model(x)
    y = torch.mean(fuse_image[0])
    loss = criterion(y, torch.tensor(1.1))
    loss.backward()