Error while running the code : RuntimeError: CUDA error: invalid device ordinal

[rudhn2001]

Hello, while running this code i get an error
" RuntimeError: CUDA error: invalid device ordinal "
CUDA kernel errors might be asynchronously reported at some other API call,so the stacktrace below might be incorrect.
For debugging consider passing CUDA_LAUNCH_BLOCKING=1.
it first shows 'start training'
then shows 'random seed : (random numbers)'
then : 'loaded pretrained model (ImageNet)'
and then comes runtime error.
can anyone please help me fix this issue,
Thank you.