Solved by pascal_notsawo in post #10 
              
              
                It seems that I have found the cause of your problem. 
self.U.parameters() is not a parameter, but a list of parameters (see comments below). 
import torch
from torch import nn
from torch.autograd import Variable

class Model(nn.Module) :
    def __init__(self, nUser, edim_u, lr = 3e-4):
        sup…