[Player] cache find_spell lookups

[seanpeters86]

This is roughly a 33% increase in speed when testing locally for shadow priest. I added a debug line when the cache is hit and it seems like almost all of these are for items or special effects. There were over 300,000 cache hits in a single iteration when testing locally.

[scamille]

My gut feeling says that we might want to rather fix the underlying code that calls find_spell so often instead of potentially increasing memory usage so significantly.

On the other hand, a 33% increase does sound lovely. How many iterations and thread did you use when getting this number?

[seanpeters86]

@scamille the root cause of most of these issues was fixed here: 7df2bff

so really the question is do we leave this in as insurance in case it happens again?

Was talking with @lgkern and @Saeldur about this and i think it would make sense to refactor this into something that simply alerts on change if you have added a significant amount of find_spells compared to previous or something.

[Dorovon]

One option might be to add a counter in debug builds with an assert (or maybe just a warning) that goes off if some excessive number of lookups occur.

[navv1234]

I don't mind having a base level cache for this stuff at least, but it's just a bit sad that we have gone from having a relatively fast (O(1)) access back in the day to having an issue with the id-based find_spell() performance-wise.

[scamille]

One option might be to add a counter in debug builds with an assert (or maybe just a warning) that goes off if some excessive number of lookups occur.

I like the idea. I think we could just generally warn on any find_spell after combat begin on iteration>0. Sure there might be some false positives for things with lazy initialization, but it would be interesting to see how bad it is.

[lgkern]

Yea, that was one idea we bounced around, to have a way for it to fail tests when find_spell is being called during iterations, that would make it easy to detect, at least after a couple of callings.