CUDAPrefetcher.py

from torch.utils.data.dataloader import _SingleProcessDataLoaderIter
class CUDAPrefetcher(_SingleProcessDataLoaderIter):
    def __init__(self, loader, device=None, priority=0):
        if not torch.cuda.is_available():
            raise Exception("Only CUDA")
        super(CUDAPrefetcher, self).__init__(loader)
        self.device = device
        self.stream = torch.cuda.Stream(device=device, priority=priority)
        self.last = None

    def __next__(self):
        torch.cuda.default_stream(device=self.device).wait_stream(stream=self.stream)
        result = self.last
        if result is None:
            result = super(CUDAPrefetcher, self).__next__()  # may raise StopIteration
            for x, d in enumerate(result):
                result[x] = d.to(device=self.device, non_blocking=False)
        try:
            self.last = super(CUDAPrefetcher, self).__next__()
            with torch.cuda.stream(stream=self.stream):
                for x, d in enumerate(self.last):
                    self.last[x] = d.to(device=self.device, non_blocking=True)
        except StopIteration:
            self.last = None
        return result

There is no acceleration.