Solved by xian_kgx in post #13 
              
              
                So you wanted to do is multi-scale training? 
Then perhaps you could do: 
for batch1, batch2, batch3 in zip(daloaders[0], dataloaders[1], dataloaders[2]):
    input1, label1 = batch1
    input2, label2 = batch2
    input3, label3 = batch3

    pred1 = model(input1)
    pred2 = model(input2)
    pred…