Yes I do.  by adding mp_location to torch.load,  the problem is solved.  What puzzled me is that  if I don’t specify mp_location in torch.load while specifying it  in outer class which call torch.load,  Pytorch1.7 run well, Pytorch1.8 report the error,   it implys that torch.load in Pytorch1.8 attemtps to load to GPU, and Pytorch1.7 not.