FID score in validation_epoch_end

[rubencart]

I want to compute the FID score for two lists of images stored on disk in different paths. I call calculate_fid_given_paths from pytorch-fid in my validation_epoch_end method.

For DDP, how do I make sure the fid isn't calculated twice? Would wrapping the contents of validation_epoch_end in a if self.local_rank == 0: make sense? PL complains with a MisconfigurationException though, because I have a checkpoint callback watching the computed fid score, and in this case the value is only logged on the main process. How do I avoid computing the same score twice correctly?