ModelCheckpoint period should not always save on the first epoch

[carmocca]

🚀 Feature

period should work so:

# ModelCheckpoint on_validation_end
if (epoch + 1) % period:
    # do not save
    return

e.g:

• period == 1: save on epoch 0, 1, 2...
• period == 2: save on epoch 1, 3, 5...
• period == 3: save on epoch 2, 5, 8...

currently, it always runs on the first epoch and then runs every period epochs

e.g:

• period == 1: save on epoch 0, 1, 2...
• period == 2: save on epoch 0, 2, 4...
• period == 3: save on epoch 0, 3, 6...

This would also allow having period = 0 which would never save, just as save_top_k = 0

Motivation

I want to save a checkpoint every period epochs but current behaviour forces to always save on the first one.

[williamFalcon]

makes sense. submit a PR?

[ananthsub]

@williamFalcon why is epoch 0-indexed in one place and 1-indexed in other places? can it be consistent across lightning instead of these +1s? I think the same issue affects batch indices too

[williamFalcon]

yes, we did a refactor a while to make everything zero indexed. where did we miss spots?