9

I am writing a C++ chess engine and I am looking for magic numbers for Little-Endian Rank-File Mapping bitboards to generate moves for sliding pieces.

The rival chess website gives magic numbers but not for the same board mapping.

The chess programming wiki gives some of the best magic numbers so far but is not exhaustive.

At the end I am looking for four things:

  • occupancy mask for each square
  • magic number for each square
  • magic shifts for each square
  • moves database array for each square

So I can use the following code to find the moves of the Rook on C3 (for instance):

bbBlockers = bbAllPieces & occupancyMaskRook[C3]

databaseIndex = (int)((bbBlockers * magicNumberRook[C3]) >> rookMagicShifts[C3])

bbMoveSquares = magicMovesRook[C3][databaseIndex] & ~bbFriendlyPieces
3
  • I believe this question will be better suited and answered at programmers.stackexchange.com or stackoverflow.com . May 7, 2015 at 22:01
  • 1
    Not really. This is still answerable here. BTW, programmers focus more on high-level abstraction. stackoverflow.com would have been better.
    – SmallChess
    May 7, 2015 at 23:36
  • @PeteBecker You are right, I changed it
    – Romain
    May 8, 2015 at 16:58

1 Answer 1

9

This is a very well known problem in chess programming. You should consider use the numbers generated by Pradyumna Kannan. Dr Kannan had kindly produced open-source the magic numbers. It is being used by Crafty and a few other chess engines including my own.

You can read more by google "Crafty magic number".

I've prepared a zipped file for you here. This is the same files being used in the SmallChess chess engine app. Please read the documentation. Basically, you'll need to call Rmagic(square, occupancy) for rooks and Bmagic(square, occupancy) for bishops. You can XOR those into a queen mask.

11
  • Thanks it works well. Can I freely use/modify this code in my chess engine?
    – Romain
    May 8, 2015 at 19:26
  • There is no licence restriction. Use as you pleased. It wasn't me who did it, it was a contribution by Dr Kannan. Please accept my answer if it helps!
    – SmallChess
    May 9, 2015 at 0:44
  • Hi, can you upload the file MagicMoves.zip to GoogleDrive? I can't download it at smallchess (I got some error). Thanks.
    – 123iamking
    Mar 23, 2020 at 4:59
  • @123iamking The link is still working. I am not going to remove it.
    – SmallChess
    Mar 23, 2020 at 4:59
  • @SmallChess - I don't ask about removing it, can you provide a mirror with Google Drive? Thanks.
    – 123iamking
    Mar 23, 2020 at 9:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.