Author: Dann Corbit
Date: 16:53:58 01/06/05
Go up one level in this thread
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? 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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