Search found 903 matches

by AlvaroBegue
Wed Jul 21, 2010 1:24 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Questions for the Stockfish team
Replies: 299
Views: 40854

Re: Questions for the Stockfish team

I haven't read the whole thread (too long!), but I see you guys are talking about random evaluation. I have looked at this (alpha-beta search with a `-10000+rand()%20001' as evaluation function) in the past, and it is true that it captures certain dynamic notion of mobility. What I wanted to mention...
by AlvaroBegue
Tue Jul 20, 2010 12:52 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Bitboard file and rank, and bitboard footprint
Replies: 6
Views: 1066

Re: Bitboard file and rank, and bitboard footprint

P.S. Side note, it seems bitboards have a larger footprint than even a plain 64bit character array. 6 pieces, 2 colors so 12 pieces at 64bits a position would be 8bytes per position so 96bytes per board state. Sound right? You probably mean "larger footprint than even a plan 64 -byte array." The an...
by AlvaroBegue
Tue Jul 20, 2010 12:49 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Bitboard file and rank, and bitboard footprint
Replies: 6
Views: 1066

Re: Bitboard file and rank, and bitboard footprint

First you need a function that will map the 64 possible inputs into small numbers. Here are three (roughly from slow/simple to fast/complex): * x%67 * ffsll(x) ( http://linux.die.net/man/3/ffsll ) * (DE_BRUIJN_MAGIC_CONSTANT * x) >> 58 Then you make use of a small look-up table that has a precompute...
by AlvaroBegue
Sun Jul 18, 2010 8:54 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Random number generating CPU
Replies: 5
Views: 1050

Re: Random number generating CPU

Pft ;) not even a new feature on x86 CPUs by a long shot. VIA Padlock has been available for what in computer terms is geological ages. Its a good idea to have it on die. Capable of creating random numbers at rates of between 800K to 1600K bits per second, the VIA PadLock RNG addresses the needs of...
by AlvaroBegue
Thu Jul 15, 2010 12:50 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Transposition table random numbers
Replies: 45
Views: 5195

Re: Transposition table random numbers

Any situation where there is a pawn on the 5th rank flanked by two opponent's pawns is ambiguous. Given how easy to fix this is, why risk it? I don't think anyone can seriously argue that en-passant info shouldn't be hashed properly. Having a separate entry in a table for each possible pawn costs yo...
by AlvaroBegue
Wed Jul 14, 2010 10:42 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Transposition table random numbers
Replies: 45
Views: 5195

Re: Transposition table random numbers

bob wrote:While I agree it is possible to have ambiguities, how often would you find the _exact_ same position, but with ep captures possible on different squares?
1. e4, d5 2. e5, f5

1. e4, f5 2. e5, d5

That wasn't so hard to imagine...
by AlvaroBegue
Wed Jul 14, 2010 3:30 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Transposition table random numbers
Replies: 45
Views: 5195

Re: Transposition table random numbers

What is 769? It seems to be 64*12+1. I guess it's just the 12 piece types (although pawns on ranks 1 and 8 shouldn't matter much) plus one for whose turn it is? If that's the case, you are missing en-passant information, which can be important (Ruy-López lost a game against Diep in WCCC'99 partly be...
by AlvaroBegue
Wed Jul 14, 2010 12:50 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: Transposition table random numbers
Replies: 45
Views: 5195

Re: Transposition table random numbers

If anyone is concerned about the randomness of the numbers in the Zobrist table (although I agree with Bob that it doesn't matter), you can come up with several tables using different methods and then XOR them together. The result will be at least as random as the most random "ingredient" you put in...
by AlvaroBegue
Thu Jul 08, 2010 3:58 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: root move ordering
Replies: 79
Views: 13594

Re: root move ordering

We also observed the program during games, and it was clear that the very last move searched turned out to be chosen surprisingly often. Are you sure it wasn't just the last move to be *finished* searching, as opposed to the last move in the array? I ask because I've been seeing that when splitting...
by AlvaroBegue
Thu Jul 08, 2010 3:19 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: root move ordering
Replies: 79
Views: 13594

Re: root move ordering

We also observed the program during games, and it was clear that the very last move searched turned out to be chosen surprisingly often. Are you sure it wasn't just the last move to be *finished* searching, as opposed to the last move in the array? I ask because I've been seeing that when splitting...