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Subject: Move ordering at root of search

Author: Tom King

Date: 13:48:41 05/07/01


Hi all,

there's been a few postings recently about strategies for programs to
effectively order moves at the root of the search. One strategy which is quite
interesting is the "order by nodes searched" heuristic, used by Crafty (and
maybe others). Currently, my program, Francesca, uses a very simple "order by
eval()" heuristic for ordering root moves.

As a test, I played a series of games between the standard version of my
program, and a version which uses a "order by nodes searched" heuristic for
ordering root moves. I set these two versions playing blitz, last night. When I
just checked, they had played 130 games, and each had scored 50%. Each had won
37, lost 37, and drawn 56. Amazing that it should end so even!

It's difficult to draw any conclusions from this.

Probably more games are needed to see if "order by nodes searched" really helps.
My hunch is that it may be a win at slower time controls - move ordering becomes
more important the deeper you search.. [this reminds me of the time back in 1995
when the move ordering in my program was very poor.. didn't seem to matter too
much at blitz, but at slower time controls, the search just ground to a halt. I
remember (fondly) how I made some improvements to Francesca's move ordering, and
suddenly she was searching throught the deeper plies 10 times quicker! Ah! great
days..]

Rgds,
Tom




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