I did a couple of experiments，it seems that more gpu more time, and setting num_workers=0 doesn’t work.
batch 8
gpus 2 num_worker 16 01:57
gpus 2 num_worker 4 01:56
gpus 2 num_worker 0 02:07
batch 8
gpus 1 num_worker 4 01：32
gpus 1 num_worker 0 01：43