Calculate train accuracy of the model in segmentation task

(Neda) #1

I think I don’t have a good understanding of train accuracy. This is the snippet for train the model and calculates the loss and train accuracy for segmentation task.

 for epoch in range(2):  # loop over the dataset multiple times
        running_loss = 0
        total_train = 0
        correct_train = 0
        for i, data in enumerate(train_loader, 0):
            # get the inputs
            t_image, mask = data
            t_image, mask = Variable(, Variable(

            # zeroes the gradient buffers of all parameters
            # forward + backward + optimize
            outputs = model(t_image) # forward
            loss = criterion(outputs, mask) # calculate the loss
            loss.backward() # back propagation
            optimizer.step() # update gradients
            running_loss += loss.item()
            # accuracy
            _, predicted = torch.max(, 1)
            total_train += mask.size(0)
            correct_train += predicted.eq(
            train_accuracy = 100 * correct_train / total_train
           #avg_accuracy = train_accuracy / len(train_loader)                                     
            print('Epoch {}, train Loss: {:.3f}'.format(epoch, loss.item()), "Training Accuracy: %d %%" % (train_accuracy))

I am getting a number like below for the training accuracy which I assume is the amount of pixel which corresponds with the ground truth (mask). is that correct?

Epoch 0, train Loss: 0.721 Training Accuracy: 500300 %
Epoch 0, train Loss: 0.707 Training Accuracy: 676000 %

How can I calculate the accuracy of the network that shows the performance of the model? (ex. The accuracy of the network on the 10000 test images: 54 % in pytorch tutorial but this is for the classification task )


You are currently summing all correctly predicted pixels and divide it by the batch size. To get a valid accuracy between 0 and 100% you should divide correct_train by the number of pixels in your batch.
Try to calculate total_train as total_train += mask.nelement().

(Neda) #3

@ptrblck yes it works. Thanks a lot

1 Like
(Vishal Singh) #5

I this piece of code of yours

# accuracy
            _, predicted = torch.max(, 1)
            total_train += mask.size(0)
            correct_train += predicted.eq(`

what are you trying to do in first line with torch.max especially why 1 and not 0. In 3rd line with predicted.eq()