Friday, 03 August 2007

Null moves

I finally got null moves to work in Vicki. I had some trouble with the capturing of the king (which caused Vicki to hang), but I eventually got it fixed. I am utterly amazed at the effect of null moves in the engine. With null moves Vicki searches (on average) 1-2 plies deeper and even more later in the game. In late-middle games, depths of 12 plies are reached! That is without any other form of pruning or transposition tables. The new version of Vicki is already playing on FICS and I am conducting tests against the older version to evaluate the improvement.

Why didn't I have this ready for the WRCC?

7 comments:

Jonatan Pettersson said...

Just a word of caution. Null moves can prune a lot of moves if you're not careful, so missing important moves is always a factor.

Make sure you test it and not get blinded by the high ply count. :) (though 1-2 plies sounds normal so you probably don't have anything to worry about)

Anonymous said...

well done!

I expect Vicki to be challenging crafty soon at this rate!

Anonymous said...

Hi Good luck with Vicki, looks like it is improving very steadily. I am guessing that you have a bug in your transposition table code, once you get that working you should see another sizeable improvement.
One thing that I never figured out with my chess program was how to make it play on a chess server like FICS. Maybe that is something you could describe on one of your blog posts ? I would be interested to read that if you could write it up in detail?

Regards Geoff

Sparky said...

It seems like null moves is still not quite correct. Often Vicki will make a terrible blunder...combined with brilliant moves... Clearly, the engine is pruning away moves that should not be. So it seems I need to work on this a bit more :-(

Transposition tables is also making everything worse. This is a nasty hurdle. If only I had more time to work on this...

Anonymous said...

any updates???

Rajiv Bakulesh Shah said...

I'm glad you're progressing, but Vicki isn't looking ahead 12 plies. Or, if she is, she's pruning way too aggressively. Either way, there's a bug. :-)

Camiseta Personalizada said...
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