Author: Robert Hyatt
Date: 20:56:23 08/26/05
Go up one level in this thread
On August 26, 2005 at 20:29:30, Brian Richardson wrote: >On August 26, 2005 at 16:14:33, Robert Hyatt wrote: > >>On August 26, 2005 at 15:57:09, Charles Roberson wrote: >> >>> >>> Bob, >>> >>> In Telepath (bitboard), I matched the ordering from NoonianChess >>>(nonbitboard). While this allowed some code reuse, it was somewhat confusing. >>> >>> The pattern was A1=0, H1=7, A2=8, H2=15 ....... >>> >>> In hind sight, It may have been better to use A1=7, H1=0, A2=15, H2=8. >>> >>> Think of each system and how mentally easy or hard it is to calculate >>> diagonals. The reason I say "mentally easy" is you have to use your own >>> brain to debug as you well know. >>> >>> Charles >> >>That is what I used in Crafty originally, which might be why many used the same >>numbering. The problem is that this requires you to "mentally" invert things, >>which is not necessarily a bad thing. I have considered keeping this the same, >>and just having to "mentally mirror" things since in a 64 bit value, bit 0 is >>the right-most bit... >> >>might be the best idea to leave the bit numbers the same, in fact... and just >>deal with the visualization issues mentally and not make that many drastic >>changes to the engine... > >Tinker also uses Crafty's bitboard numbering (albeit non-rotated), and yes, >sometimes it is a bit of a pain to visualize... >But, I would just like to suggest some caution about the bitboard renumbering >idea. They are used in soooo many places and there are mask constants and such >all over; missing just one will mess things up in hard to find ways. I >understand that you will be essentially rewriting the eval, but even so it is >just hard to see the benefit relative to the risk, IMO. I had actually already reached that decision, looking at the code. Much was pretty easy to change, but changing all the rotated bitmap stuff is a pain, and even pawn move generation would be altered. So I've scrapped this, and will just continue to put up with 63-square for the BSF/BSR stuff. :)
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