Author: Daniel Shawul
Date: 05:14:40 06/14/04
Go up one level in this thread
On June 13, 2004 at 16:46:14, Tord Romstad wrote: >On June 13, 2004 at 14:24:57, GeoffW wrote: > >>Hi >> >>I was thinking how I would add pawn hashing to my program. Having read a little >>of the Crafty source I have a rough grasp of the idea, however there are a >>couple of things I am hazy on. >> >>Q1) >>I understand the pawn hash score stored must not contain any piece related >>scoring as that must be factored in later. In my program even the simple choice >>of which pawn position look up table is determined by the phase of the game, i.e >>it will be piece dependent. How would I get over that obstacle ? Score the pawns >>for end game, opening and middle in the hash, and choose which one to use later >>? > >I don't store any scores at all in the pawn hash table, but just lots of >computations >which is used by the evaluation function. I store things like the location of >all >passed, isolated, double or backward pawns, pawn chains, number of pawns on >black/white squares for both sides, a classification of the centre (open, >closed, >semi-closed, etc.), and so on. > >>Q2) >>Crafty uses an 8 bit bitmap to store file for passers, this is ok for a bitboard >>program as it is probably trivial to find the exact location later. However for >>a non bitboard program it is non trivial to find the exact locations. Do I have >>any alternative but to store the passer locations in the hash ? That would be 16 >>bytes just for the passed pawns for both sides? > >My program also doesn't use bitboards. I simply store all the exact locations. >This is not a problem, you can afford to use lots of space for your pawn hash >table entries. My entries are 128 bytes big. Keep in mind that the number of I totally agree with you.Neither the size of the entry nor the number of entries seems to bring a significant difference. I suddenly increased the entry size by 2 big arrays (20 bytes),and i didn't notice significant slow down. My prog now uses 2M(65536 entries) by default. daniel >pawn structures seen in a single search isn't very big, and that this means that >you don't need to store a big number of entries. I found that increasing the >pawn hash table size beyond 256 entries gave only a tiny increase in speed >(about 3%, IIRC). > >Tord
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.