Jan 21, 2009

[Other] Evaluation "problem"

One of the (many) bugs I've discovered while working with Mediocre the last month was that it uses the wrong piece square tables for the most part of the games.

Mediocre has two kinds of tables, for opening/middle game and for endings.

The bug was that Mediocre changed to ending tables after the opening phase. That is awarding moving the king and queen into the center etc. in the middle game...

The weird part is that this greatly improves the performance of Mediocre. "Fixing" the bug in v0.334 and running a match against a non-fixed version results in a clear victory for the latter.

I assume this has to do with the mobility/piece square features not being scaled as they should.

I will have to take a long look at the evaluation again since this is clearly a bad thing. :)


Anonymous said...

Are you basing this off of one game? You need a good number of games before determining which evaluation scheme is statistically more effective.

Jonatan Pettersson said...

A bit later answer, and obviously I can't remember exactly what I did here.

But my terminology is game=one game, match=many games.

Of course back when this was written "many games" was usually 20 1-minute games (without increment).

So probably not a valid test anyway.