def _batch_unshuffle_ddp()

in moco/builder.py [0:0]

• 8 lines of code
• 2 McCabe index (conditional complexity)

    def _batch_unshuffle_ddp(self, x, idx_unshuffle):
        """
        Undo batch shuffle.
        *** Only support DistributedDataParallel (DDP) model. ***
        """
        # gather from all gpus
        batch_size_this = x.shape[0]
        x_gather = concat_all_gather(x)
        batch_size_all = x_gather.shape[0]

        num_gpus = batch_size_all // batch_size_this

        # restored index for this gpu
        gpu_idx = torch.distributed.get_rank()
        idx_this = idx_unshuffle.view(num_gpus, -1)[gpu_idx]

        return x_gather[idx_this]