Author: Daniel Shawul
Date: 01:15:37 01/07/05
Go up one level in this thread
On January 06, 2005 at 19:53:58, Dann Corbit wrote: >On January 06, 2005 at 19:15:58, Pallav Nawani wrote: > >>On January 06, 2005 at 18:18:40, David B Weller wrote: >> >>>Hi Geoff, >>> >>>The fact that you stumble over my code is probably a credit to your >>>intellegence, and if I tried to explain: attack_mask[][], I would embarass >>>myself. >>> >>>In fact, while thinking over how to best answer your question, I too became >>>somewhat puzzled as to how what I did, actually improves GES performance. It >>>really is inacurate. >>> >>>The part I added is at the end of control.cpp and 1 line in evaluate.cpp : >>> >>>s += count_ctrl() * 3; >>> >>> the '3' is pulled from memory - I think Prof Hyatt used it for Bishop mobility, >>>but since what I am counting isnt the same, it is probably way off. WAY off. >>> >>>The basic idea of count_ctrl() is to detirmine who 'owns' each of the 64 >>>squares. But it is very simple and naive. It makes assumptions which are >>>probably true more often than not, but still wrong much of the time. eg., if >>>white has a pawn attacking a square, but black doesnt have a pawn attacking that >>>square - white owns the square. regardless of what else is attacking it. If both >>>have pawns attacking [or, niether do] then the same idea is applied for knights. >>>Then Bishops, then Rooks, then Queens. >> >>So what you are evaluating is board control. I had no idea it was that useful. >>Maybe I will try implementing that (after I have implemented attack tables, that >>is). > >A bitboard program will have a stupendous advantage here [considering again >Fabian's code]. > >If you look at the eval function (where he calculates mobility) with a bitboard >program you can precompute EVERYTHING and every single nested loop goes away. > >By a stupendous margin, all of his program's time is bottled up by eval(). > >If Fabian's program were converted to bitboard, it could run 5x faster. How's >that for a scary thought? Hi Dann 5x faster is probably an exaggeration. I have my self a copy of evaluation function without attack tables(ie using attack functions). When i use that one it increases NPS by <=100000 which is 25% speed up. Besides if you are going to use bitboards you loose all the nice evaluation you can do with the attack tables. King Safety and Square control are some examples. As demonstrated on Ed's page it is even possible to SEE. With bitboards it is only possible to compute a fair mobility fucntion but no more. best daniel > >It might be possible to do the same precomputations using a 0x88 format, but I >would have no idea how to accomplish it. With bitboards, it is trivial.
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