In Pytorch, if I have a 2D tensor, how to iterate over this tensor to get every value changed

Question

I have a 2d Tensor, whose size is 1024x1024 and the values in the tensor is 0.3333, 0.6667, and 1.0000, so I would like to change all these values to 0,1,2.

Could some one tell me how to iterate over this tensor.