One of the variables needed for gradient computation has been modified by an inplace operation for this specific piece of code

Linux_Penguin: <p>Hi, I am new to AI and decided to use Pytorch. I want to this model to generate some images, however as this was written before Pytorch 1.5, since the gradient calculation has been fixed then, this is the error message.</p>
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<p>RuntimeError: one of the variables needed for gradient computation has been modified by an inplace operation: [torch.cuda.FloatTensor [1, 512, 4, 4]] is at version 2; expected version 1 instead. Hint: enable anomaly detection to find the operation that failed to compute its gradient, with torch.autograd.set_detect_anomaly(True).&lt;&lt;&lt;</p>
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<p>I have looked at past examples and am not sure what is the problem, I believe it is happening within this region but I don’t know where! Any help would be greatly appreciated!</p>
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<p>def process(self, images, edges, masks):<br>
self.iteration += 1</p>
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<pre><code>    # zero optimizers
    self.gen_optimizer.zero_grad()
    self.dis_optimizer.zero_grad()


    # process outputs
    outputs = self(images, edges, masks)
    gen_loss = 0
    dis_loss = 0


    # discriminator loss
    dis_input_real = torch.cat((images, edges), dim=1)
    dis_input_fake = torch.cat((images, outputs.detach()), dim=1)
    dis_real, dis_real_feat = self.discriminator(dis_input_real)        # in: (grayscale(1) + edge(1))
    dis_fake, dis_fake_feat = self.discriminator(dis_input_fake)        # in: (grayscale(1) + edge(1))
    dis_real_loss = self.adversarial_loss(dis_real, True, True)
    dis_fake_loss = self.adversarial_loss(dis_fake, False, True)
    dis_loss += (dis_real_loss + dis_fake_loss) / 2


    # generator adversarial loss
    gen_input_fake = torch.cat((images, outputs), dim=1)
    gen_fake, gen_fake_feat = self.discriminator(gen_input_fake)        # in: (grayscale(1) + edge(1))
    gen_gan_loss = self.adversarial_loss(gen_fake, True, False)
    gen_loss += gen_gan_loss


    # generator feature matching loss
    gen_fm_loss = 0
    for i in range(len(dis_real_feat)):
        gen_fm_loss += self.l1_loss(gen_fake_feat[i], dis_real_feat[i].detach())
    gen_fm_loss = gen_fm_loss * self.config.FM_LOSS_WEIGHT
    gen_loss += gen_fm_loss


    # create logs
    logs = [
        ("l_d1", dis_loss.item()),
        ("l_g1", gen_gan_loss.item()),
        ("l_fm", gen_fm_loss.item()),
    ]

    return outputs, gen_loss, dis_loss, logs

def forward(self, images, edges, masks):
    edges_masked = (edges * (1 - masks))
    images_masked = (images * (1 - masks)) + masks
    inputs = torch.cat((images_masked, edges_masked, masks), dim=1)
    outputs = self.generator(inputs)                                    # in: [grayscale(1) + edge(1) + mask(1)]
    return outputs

def backward(self, gen_loss=None, dis_loss=None):
    if dis_loss is not None:
        dis_loss.backward()
    self.dis_optimizer.step()

    if gen_loss is not None:
        gen_loss.backward()
    self.gen_optimizer.step()&lt;&lt;&lt;
</code></pre>

Sayed_Nadim: <p>Hi,<br>
Can you train the generator first and then the discriminator? The discriminator seems to detach the output from graph for loss calculations.</p>

Linux_Penguin: <p>Thank you for the solution!</p>