Zobrist free

[Henk]

I went back to my old bitboard key. Disadvantage is that it's slower and also costs more memory.

Code: Select all

   public Key(IChessBoardBits board)
        {
            rep = new ulong[SIZE];
            rep[0] = board.Pawns;
            rep[1] = board.Kings;
            rep[2] = board.Knights;
            rep[3] = board.Bishops;
            rep[4] = board.Rooks;
            rep[5] = board.Queens;
            rep[6] = board.WhitePieces;
            rep[7] = board.Other;
        }

[Ras]

I went back to my old bitboard key. Disadvantage is that it's slower and also costs more memory.

On the upside, this means that the NSA has more problems hacking the key.

[Henk]

Yes I used the last position of the last game I played at 31-12-2016 to generate my password for my account.

By the way I only had to fix a few hundred compile errors and a bad run time error to change it back. Talking about maintainable software.

[Ras]

Talking about maintainable software.

Uhm.. version control / backup? Even just saving the whole folder into a ZIP archive named by date may work.

[stegemma]

Really? Why?

[Henk]

I wanted to eliminate the risk of a hash collision. So if there is a bug or a bad move being played I can be sure it's not because of that. May be 8 x 64 bits is a bit too expensive.

[stegemma]

For this I add the FEN string to the TT entries when I want to test for collisions; that make easier to debug (it slows down the program more than your solution, of course).

Another way could be to just add an extra hash value of the whole 8x64 bits, maybe with sum/rotations, so to have a single extra 64 bit key.

[Henk]

I also did not like the code I created for Zobrist key. With bit boards key you don't have to update the key for that has already been done.

Don't know what is the minimal size for a complete key. Probably about 4 x 64 bits I guess.

[AlvaroBegue]

I also did not like the code I created for Zobrist key. With bit boards key you don't have to update the key for that has already been done.

Don't know what is the minimal size for a complete key. Probably about 4 x 64 bits I guess.

4 x 64 bits is 256 bits. John Tromp has a proof that the number of chess diagrams is at most 2^155. So you can do better than 256 bits, even after you take castling rights and en-passant state into account.

[Pio]

Hi Henk!

I save my board in 3*64 = 192 bits but you can do it more efficiently. See my post http://www.talkchess.com/forum/viewtopi ... 93&t=49575

You can also see the quad board representation on the superb chess programming wiki if you want a compact and fast representation.

/Pio