why loss is nan

[Tom-zgt]

[Tom-zgt]

loss=nan (nan): : 0% 0/100 [00:00<?, ?it/s]NaN or Inf found in input tensor. loss=nan (nan): : 2% 2/100 [00:00<00:07, 12.49it/s]NaN or Inf found in input tensor. loss=nan (nan): : 2% 2/100 [00:00<00:07, 12.49it/s]NaN or Inf found in input tensor. loss=nan (nan): : 4% 4/100 [00:00<00:07, 12.77it/s]NaN or Inf found in input tensor. loss=nan (nan): : 4% 4/100 [00:00<00:07, 12.77it/s]NaN or Inf found in input tensor. loss=nan (nan): : 6% 6/100 [00:00<00:07, 13.24it/s]NaN or Inf found in input tensor. loss=nan (nan): : 6% 6/100 [00:00<00:07, 13.24it/s]NaN or Inf found in input tensor. loss=nan (nan): : 8% 8/100 [00:00<00:06, 13.48it/s]NaN or Inf found in input tensor.