Author: Joel
Date: 07:53:05 11/17/02
Hey All, I am a 2nd year Uni student from Australia who has recently gotten into chess programming. My first attempt was a simple array-based alpha-beta variant which struggled to search more than 6 levels deep in most positions! I think that might have something to do with the fact that there was no move ordering, transposition table, an expensive evaluation function, no killer moves and weak coding :) I have been working on my second attempt for some time now. It uses Bitboards. I have a few questions regarding move generation. It seems to me that the performance of the Bitboard approach relies somewhat heavily on how fast you can retrieve the position of a 1 bit within a 64-bit unsigned integer. I looked for sometime on the Internet for some kind of magical, hacky solution to this dilemna, and the best I could find was this (b & -b) trick which I used in a debatedly clever way. I was just wondering if there is any approach significantly better than the one which I will outline below: 1. (b & -b) to clear all 1 bit's except for one. 2. get this value, mod it by 67 (which has the property that every possible value returned is unique, thus i can hash to the position of the bit in the 64 bit integer.) I am no expert, but it doesn't seem too ineffecient to me. Any problems? Also, if there are any improvements, I would prefer to find out about the ones which do not involve assembly coding - I do not want to make my program too dependant on any one CPU architecture at this stage. Thanks for your time, Joel
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