Author: Tony Werten
Date: 01:51:39 06/20/00
Go up one level in this thread
On June 20, 2000 at 04:48:05, James Robertson wrote:
>On June 20, 2000 at 04:44:57, Tony Werten wrote:
>
>>On June 20, 2000 at 03:50:36, James Robertson wrote:
>>
>>>On June 20, 2000 at 03:09:49, Tony Werten wrote:
>>>
>>>>On June 19, 2000 at 19:54:39, James Robertson wrote:
>>>>
>>>>>On June 19, 2000 at 19:48:36, Larry Griffiths wrote:
>>>>>
>>>>>>I have found bitboards to be an even trade-off on my Pentium system. I have to
>>>>>>update about 6 bitboards when a piece moves and this generates a lot of
>>>>>>instructions. I get it back in my IsKingInCheck code so it evens out.
>>>>>
>>>>>While detecting check is faster with bitboards if you have many pieces on the
>>>>>board, I think it is actually slower in endgame positions. :(
>>>>
>>>>I don't understand this. I have written it before but here it is again. You only
>>>>have to look at the to and from square of the last move.
>>>
>>>I do not understand.... could you please elaborate?
>>
>>Sure,
>>
>>If you exclude a rochade, a check can only occur in 2 ways.
>>
>>1) The piece last moved is giving check ( on the to-square )
>>2) The piece just moved revealed a slider which is giving check. ( behind the
>>from square )
>>
>>The code should look something likes this. ( there might be some mistakes)
>>
>>if (last_move==rochade)
>>{
>> square=king_square;
>> if (possible to attack square from rook_square)
>> {
>> repeat
>> square+=dir_of_rook;
>> until (square!=empty)
>> }
>> return (square==rook_square)
>>}
>>
>>if (possible for moved_piece to attack king_square from to_square)
>>{
>> if moved_piece==KING,KNIGHT or PAWN then return (true)
>> square=king_square;
>> repeat
>> square+=dir_of_to_square;
>> until (square!=empty)
>> if (square==to_square return) (true)
>>}
>>
>>if (possible for BISHOP or ROOK to attack king_square from from_square)
>>{
>> square=king_square;
>> repeat
>> square+=dir_of_from_square;
>> if (square!=empty) then return (piece_on_square can attack king_square)
>> until (square is not on board)
>>}
>>
>>return false;
>>
>>cheers,
>
>
>This idea looks nice. I think I can use it to improve my existing code....
>Thanks!
You're welcome. But I prefer if you let me win on the next dutch championships.
Tony
>
>James
>
>>
>>Tony
>>
>>PS If you are looking for a selfcheck, you only have to do the from_square. ( If
>>you didn't start of in check )
>>
>>>
>>>Thanks,
>>>James
>>>
>>>>
>>>>It has nothing to do with the number of pieces.
>>>>
>>>>Tony
>>>>
>>>>>
>>>>>James
>>>>>
>>>>>> I like
>>>>>>to have fast move generation code, but most of my gains have been through
>>>>>>alpha-beta, hash-table, killer-move and movelist ordering etc.
>>>>>>
>>>>>>Larry.
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