Well it seems that adding that flag like I thought didnt activate the stack trace for CPP (maybe I need to build on colab?) !TORCH_SHOW_CPP_STACKTRACES=1 python pytorch-xla-env-setup.py --apt-packages libomp5 libopenblas-dev 3
so updated a little the code for some extra direct links to the code that is called when it uses fit 1 I copied the code of one batch there and @patched the Learner, so it uses this versions that have “prints” instead of the original, so internally fit calls this modified one_batch.