Hi @tinan5. Oh thats interesting. Are you by any chance reading/writing data from/to a pickle file or hdf5 file? For me this was mostly the issue. In my __init__ method, I was previously writing data as a pickle file. When I removed this, my code works fine. I guess its a issue with reading and writing files during multiprocessing. I found this issue Data Loader does not work with Hdf5 file, when num_worker >1 · Issue #11929 · pytorch/pytorch · GitHub 5 to be quite similar. Please let me know if you get any more insights.
Also you could try with the nightly version. It fixed most of the other issues which were giving the same error for me.