smart battles

So I'm planning to implement smart battle selection this weekend. Every bot (or bot set) will get at least two battles, then I will choose battles to run (in batches since I don't want idle threads) based on trying to decrease standard error in the least amount of time. Maybe with some random battles sprinkled in as well.

I'm thinking I will choose bots with the highest value for: <math>{{stDev \over \sqrt{numBattles}} - {stDev \over \sqrt{numBattles + 1}}} \over {avgBattleTime}</math>

I think this will lead to an overall result with the highest confidence in the least amount of time.

I like testing against a test bed with an average score about the same as my RoboRumble APS. The problem with this is it includes a lot of bots with super low variance (eg, 99.9% scores), so running lots of battles against them is a waste of time. But ignoring them and using a stronger test bed risks specializing against stronger bots.

That looks like a good metric for choosing fast stability. Now I'm wishing I'd included variance in the LiteRumble scores...

Yeah, do you just store a running tally of average score? I'll need to update RoboRunner to keep scores from every individual battle, too, along with battle times.

Yeah, I do a online mean calculation, so newMean = oldMean*(n/(n+1)) + newScore/(n+1), n++

I've actually thought quite a bit about this, and it all depends what score you're trying to stabilise. If you're trying to stabilise the PL, for instance, you need to run lots of battles for pairings at or near the 50/50 mark. If you're doing Schultz then lots of battles need to go to where a weak bot beat a strong bot. It's all about which battle has the most potential influence.

Yeah, for sure you would focus on different battles to optimize other rankings. I'm not sure I need to add a "focus on win/loss" flag to RoboRunner, since you'd probably just test against your toughest matchups if that's what you were working on. It does support smart battles for all the score types, though (eg survival, bullet damage).

If we do implement this type of smart battle selection in a rumble system, maybe we could have a client side setting for what you're interested in optimizing. =) I guess to start it would just be APS vs win/loss, but it could include Schultz or Vote at some point.

Got this working, just dogfooding it a bit myself before posting it since it's a pretty major change. Data files are now (gzipped) XMLs with the raw scores from every battle and everything's recalculated on the fly. (That was actually most of the work.) Comes out to about 100 kb for 3k battles.

It runs 2 seasons vs each bot then does smart battle selection with the formula above to try to increase overall accuracy as quickly as possible. It's nice to see test runs where only 2 battles were run vs HawkOnFire. =) 5% of the time, it instead chooses randomly among the bots with fewest battles, to try to mitigate cases where the variance was randomly low in the initial battles. (I can make this configurable if/when anyone cares.)

It won't schedule two battles vs the same bot unless the number of bots is <= the number of threads. Otherwise, you'd keep scheduling that bot until the battle finishes. I could instead estimate how many times in a row it would still be worth scheduling it, but that seems like a lot of work for a corner case.

I think this is going to save a heck of a lot of CPU time. The XML data files will also make it easier to let you store arbitrary score data in the custom scoring stuff.

Though I'm still figuring out how to avoid potentially corrupting the data file if you ctrl-C your run. I'm not sure if skipping the gzipping would help or if it's just become more likely because the data files are so much larger. Maybe I need to add a keyboard option to safely exit.

Just a quick node. Maybe you know that already but you can add a shutdownhook to the runtime thread. This would catch CTRL-C and you can clearly shutdown the gzipping. Not sure if that is what you looking for.

Cool, yeah, that might do the trick. I'm trying just doing a fresh save of the score data in the shutdown hook and I'll see if I can ever replicate the problem.

Still getting the feel for how many seasons to run with smart battles. It indeed seems to be much more accurate in less time, but I'm not sure to what degree I should:

• Run less seasons because it's more accurate per number of battles.
• Run the same number of seasons, since it will run faster and still be more accurate.
• Run more seasons, in about the same amount of time as before, but with much more accuracy.

I guess it partly depends on how patient you were being before this feature. =)