I got this error when trying to run https://github.com/petuum/adaptdl/tree/master/examples/pytorch-cifar 13. This seems to be a randomly happening error. I tried different versions of Pytorch (1.6, 1.7, 1.7.1) but the error is still here. In the end I got around it by setting CUDA_VISIBLE_DEVICES="0" to disable DDP.