Author: Uri Blass
Date: 02:08:08 03/23/04
Go up one level in this thread
On March 23, 2004 at 04:42:31, Uri Blass wrote: >On March 23, 2004 at 02:00:13, Mridul Muralidharan wrote: > >>On March 22, 2004 at 19:30:35, Anthony Cozzie wrote: >> >>>On March 22, 2004 at 17:18:49, Dann Corbit wrote: >>> >>>>On March 22, 2004 at 16:18:19, Anthony Cozzie wrote: >>>> >>>>>On March 22, 2004 at 03:40:57, Daniel Shawul wrote: >>>>> >>>>>>Hello >>>>>> >>>>>>I have decided to use attack tables. I just did >>>>>>a rough implementation of it at the beginning of the eval >>>>>>according to Ed's paper. The problem is the thing dropped the nodecount >>>>>>by almost 40% . Initial position nodecount was 800000 and now it is 500000. >>>>>>Do incremental move attack tables help? And how do i update the table? It seems >>>>>>very difficult to update a sliding move and other special cases. >>>>>> >>>>>>thanks >>>>>>daniel >>>>> >>>>>I have some code for incremental attack tables if you want it. However, it took >>>>>Tord 4 months to figure out :) I don't use attack tables in Zappa; i wrote this >>>>>when i was considering switching to a piecelist based engine. >>>> >>>>Is your code 0x88 or bitboard based? >>> >>>board[64]. Its based on Vincent's move generator. >>> >>>anthony >> >>Hi Anthony, >> >> I had done an incremental attacktable but was not quiet sucessful with it - it >>was almost same speed as the previous one : and so removed - potential for more >>bugs (kiss). > >I am very surprised to read it because my attack table was extremely slow and >this is the reason that I worked months on updating them incrementally. > >Calculating the directions that every square is attacked by white and black >from scratch is very expensive. > >It means doing a loop on all squares of the board after every move and for every >square doing a loop on all directions to see the direction that it is attacked >and the square of the attacker from every direction. > >Uri When I think about it again it is possible that you started with piece list so you only need to do loop on the pieces of both sides to find the attacked squares and it is cheaper. When I started I had no piece list so calculating the attack tables by loop on all the squares was very expensive. My attack tables also do not include information about the attackers but only about direction of attacks and for every direction the square of attack. At that time I thought about the idea of having a code that is also relevant for bigger board and this is the reason that I decided about direction information but later I decided to leave this idea and decided that the problem of chess is hard enough and it is better if I do not try to do the code more general. Uri
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