About prefetcher dataloader question

[523997931]

Hello,
I'd like to know what is prefetcher, in my opinion, prefetcher means pre load the picture, so train can be faster.
But I try to change train scripts, because I want to try the progressing learning( different epoch has different input-size), so I put the loader in the for loop, but I found it can't use, but if I forbid the prefetcher, it can work well, I'd like to know why.

[rwightman]

I don't think prefetcher would get in the way of that, prefetcher takes care of a few of the last items in the transform chain, so using it changes the transforms a bit. There is a small boost from using it but if you can't figure out how to use it with your changes it is fine to disable it, see case in train script and create_loader/transforms where --no-prefetcher flag is used.