fix: DataLoader freeze

.github/workflows/scripts/run-tutorial-notebook.sh

@@ -23,6 +23,12 @@ time {
 echo "::endgroup::"
 
 cd "$working_directory"
+
+# Prevent DataLoader from freezing during training.
+# https://github.com/pytorch/pytorch/issues/15808#issuecomment-1291514752
+export OMP_NUM_THREADS=1
+export MKL_NUM_THREADS=1
+
 # We may set a timeout (for each cell) to ensure in-progress notebooks and logs are saved,
 # even if the workflow hits the total 6-hour limit in GitHub Actions.
 if [ "$timeout" -ne 0 ]; then