Validation sanity check

Hi, I am new to pytorch lightning. Can someone explain what is validation sanity check ?
Thanks in advance!

You do not want run an entire training loop (could take hours) and then realise that there is a problem in your validation loop. This development process is slow and bug-prone, so we run a small validation sanity check to make sure that your code is fine before actually start training the model.

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What exactly does it check?

  1. Does it run the eval code for one batch?
  2. How can I turn it off ?
  3. What is num_sanity_val_steps parameter do? In my code it’s -1 but it still does the entire validation sanity check.

It would be a great help if you can also point me to the code/documentation.

Thanks a lot!

the integer value defines the number of validation steps you want to run.
Check the docs here.