When I write code, I find a thing that when I just use one gpu, I can use one-gpu setting: model = model.cuda(), all the things go well. Also, if I use multi-gpu setting:  model = nn.DataParallel(model, device_ids=[0]).cuda(), all the things go well too.
So what’s the difference between using  multi-gpu setting and using one-gpu setting? Like memory performance,  computation performance…