Why is Pytorch Lightning `validation_step` executed more oftener than defined in `val_check_interval`?

Question

I have a dataset with 20 rows and want to have four times a Pytorch Lightning validation_step called on this dataset. I am setting my

`val_check_interval=0.25`, 
`eval_batch_size=4` and 
`num_train_epochs=1`

. Thats my validation_step:

def validation_step(self, batch, batch_idx):
    print("+"* 30)

What I expect is to see the print command four times because of the val_check_interval instead the print appears seven times. Why is this the case?

Asked By: Max Hager

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Source

Answer 1

You need to set the value num_train_epochs to 4 to print 4 times. Currently validation_step is being called 20 times as the value of epoch is 1

val_check_interval and eval_batch_size don’t determine the validation_step calls.

use val_check_interval for validation > 1 per training epoch
Use check_val_every_n_epoch for validation for lower frequency

Answered By: Bijendra

Why is Pytorch Lightning `validation_step` executed more oftener than defined in `val_check_interval`?

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