More options in events filtering

[vfdev-5]

🚀 Feature

The idea is coming from this discussion: Project-MONAI/MONAI#5958 (reply in thread)

We would like to support the following use-cases:

1. before/after can work together with every

event = Events.ITERATION_COMPLETED(after=9, before=21, every=5)
# execute for iterations [10, 15, 20]

2. once can accept list of values

event = Events.ITERATION_COMPLETED(once=[5, 8, 23])
# execute once for iterations 5, 8 and 23

How to help with this issue

Events filtering logic is coded here:

ignite/ignite/engine/events.py

Lines 50 to 119 in 5d344a0

	def __call__(
	self,
	event_filter: Optional[Callable] = None,
	every: Optional[int] = None,
	once: Optional[int] = None,
	before: Optional[int] = None,
	after: Optional[int] = None,
	) -> "CallableEventWithFilter":
	"""
	Makes the event class callable and accepts either an arbitrary callable as filter
	(which must take in the engine and current event value and return a boolean) or an every or once value
	Args:
	event_filter: a filter function to check if the event should be executed when
	the event type was fired
	every: a value specifying how often the event should be fired
	once: a value specifying when the event should be fired (if only once)
	before: a value specifying the number of occurrence that event should be fired before
	after: a value specifying the number of occurrence that event should be fired after
	Returns:
	CallableEventWithFilter: A new event having the same value but a different filter function
	"""
	if (
	sum(
	(
	event_filter is not None,
	every is not None,
	once is not None,
	(before is not None or after is not None),
	)
	)
	!= 1
	):
	raise ValueError("Only one of the input arguments should be specified except before and after")
	if (event_filter is not None) and not callable(event_filter):
	raise TypeError("Argument event_filter should be a callable")
	if (every is not None) and not (isinstance(every, numbers.Integral) and every > 0):
	raise ValueError("Argument every should be integer and greater than zero")
	if (once is not None) and not (isinstance(once, numbers.Integral) and once > 0):
	raise ValueError("Argument once should be integer and positive")
	if (before is not None) and not (isinstance(before, numbers.Integral) and before >= 0):
	raise ValueError("Argument before should be integer and greater or equal to zero")
	if (after is not None) and not (isinstance(after, numbers.Integral) and after >= 0):
	raise ValueError("Argument after should be integer and greater or equal to zero")
	if every is not None:
	if every == 1:
	# Just return the event itself
	event_filter = None
	else:
	event_filter = self.every_event_filter(every)
	if once is not None:
	event_filter = self.once_event_filter(once)
	if before is not None or after is not None:
	event_filter = self.before_and_after_event_filter(before, after)
	# check signature:
	if event_filter is not None:
	_check_signature(event_filter, "event_filter", "engine", "event")
	return CallableEventWithFilter(self.value, event_filter, self.name)

We would like to update the following functions:

ignite/ignite/engine/events.py

Line 110 in 5d344a0

event_filter = self.once_event_filter(once)

and

ignite/ignite/engine/events.py

Line 113 in 5d344a0

event_filter = self.before_and_after_event_filter(before, after)

such that we could cover proposed use-cases. Finally, we need to write few tests here: https://github.com/pytorch/ignite/blob/master/tests/ignite/engine/test_custom_events.py

[DeepC004]

@vfdev-5 I would like to work on the issue. Please assign it to me.

[vfdev-5]

@vfdev-5 I would like to work on the issue. Please assign it to me.

@DeepC004 go ahead and work on this issue. Please detail which use-case you will work on.
I'm not assigning people on this issue as multiple people can work on that.

[DeepC004]

I can take up implementation of once as referred in the example above. From the discussion Project-MONAI/MONAI#5958 (reply in thread), once can be of type int | list[int] so I need to add the functionality of once being of type list[int] in the current implementation?

[vfdev-5]

You need to extend current behavior by adding new supported type