Optimizer parameters missing in Pytorch
I have 2 nets sharing one optimizer using different learning rate. Simple code shown as below:

optim = torch.optim.Adam([
{'params': A.parameters(), 'lr': args.A},
{'params': B.parameters(), 'lr': args.B}])


Is this right? I ask this because when I check parameters in optimizer (using code below), I found only 2 parameters.

for p in optim.param_groups:
outputs = ''
for k, v in p.items():
    if k is 'params':
        outputs += (k + ': ' + str(v[0].shape).ljust(30) + ' ')
    else:
        outputs += (k + ': ' + str(v).ljust(10) + ' ')
print(outputs)


Only 2 parameters are printed:

params: torch.Size([16, 1, 80])        lr: 1e-05      betas: (0.9, 0.999) eps: 1e-08      weight_decay: 0          amsgrad: False

params: torch.Size([30, 10])           lr: 1e-05      betas: (0.9, 0.999) eps: 1e-08      weight_decay: 0          amsgrad: False


Actually, 2 nets have more than 100 parameters. I thought all parameters will be printed. Why is this happening? Thank you!

You only print the first tensor of each param groups:

if k is 'params':
    outputs += (k + ': ' + str(v[0].shape).ljust(30) + ' ')  # only v[0] is printed!


Try and print all the parameters:

if k is 'params':
    outputs += (k + ': ')
    for vp in v:
        outputs += (str(vp.shape).ljust(30) + ' ')

