What’s your PyTorch version? It should accept a single GPU. How is that even possible that it uses last two GPUs if you specify device_ids=[0,1]?
If you run your script with CUDA_VISIBLE_DEVICES=2,3 it will always execute on the last two GPUs, not on the first ones. I can’t see how that helps in this case. CUDA_VISIBLE_DEVICES=0,1 would make more sense.