Filters don't work on custom events

[amatsukawa]

CallableEventWithFilter does not work with custom events:

from ignite.engine import Engine, EventEnum
    
def train_step(engine, batch):
    engine.fire_event(TestEvents.TEST_EVENT)
engine = Engine(train_step)

class TestEvents(EventEnum):
    TEST_EVENT = 'test_event'
engine.register_events(*TestEvents)

@engine.on(TestEvents.TEST_EVENT(every=100))
def foo(engine):
    print("hello world")

def forever():
    while True:
        yield 0.
    
engine.run(forever(), max_epochs=10, epoch_length=1)

The error is:

RuntimeError: Unknown event name '<event=TEST_EVENT, filter=<function CallableEventWithFilter.every_event_filter.<locals>.wrapper at 0x7fb7d1244710>>'

[amatsukawa]

The issue appears to be some dependence on this map here:

ignite/ignite/engine/events.py

Line 356 in 3c8b781

event_to_attr = {

I have not dug through the code to see what the dependence actually is, but it seems I should be able to do every=100 on custom events that are not necessarily bound to iteration or epoch lengths.

[vfdev-5]

Hey @amatsukawa, nice to see you here again :) thanks for reporting, I'll take a look !

[vfdev-5]

Well, it is a usage issue and bad documentation. Here is how it should be

from ignite.engine import Engine, EventEnum
    

class TestEvents(EventEnum):

    TEST_EVENT = 'test_event'

    
def train_step(engine, batch):
    engine.fire_event(TestEvents.TEST_EVENT)
    engine.state.test_event += 1
    
    
engine = Engine(train_step)
engine.register_events(*TestEvents, event_to_attr={TestEvents.TEST_EVENT: "test_event"})


@engine.on(TestEvents.TEST_EVENT(every=3))
def foo(engine):
    print("hello world", engine.state.test_event)


def forever():
    while True:
        yield 0.
    
engine.run(forever(), max_epochs=10, epoch_length=1)

As we want to filter out events, we have to have event counters and thus define a map between event name and state attribute which should be also incremented...
I'd like to refactor a bit Engine class such that counters are automatically incremented, but this is still WIP.

[amatsukawa]

Ah, awesome! Thanks for the clarification!

[amatsukawa]

Actually @vfdev-5 just want to confirm one thing: is it necessary to increment engine.state.test_event as you have done, and what are the rules on the value string in the enum, and the value of event_to_attr (does it refer to the property of engine.state, the value string of the enum, or both?)

[vfdev-5]

Yes, currently it is necessary to increment state's attribute as we check when to skip handlers trigerring according to engine.state.test_event. The str value in enum class : TestEvents.TEST_EVENT == 'test_event' is event's unique id and can be anything. Just in my example its value is accidentally the same as for state's attribute. But for example for Events.EPOCH_COMPLETED == "epoch_completed", its state attribute is state.epoch. Same for the custom event. We registered the mapping between event and state's attribute by

engine.register_events(*TestEvents, event_to_attr={TestEvents.TEST_EVENT: "test_event"})

and this engine.state.test_event = 0 was initialized.

[jrieke]

I added some docs changes in #1587. @vfdev-5 Please have a look if that works out, then I can re-create the docs and finish the PR.