Author: Gerd Isenberg
Date: 15:27:35 09/09/02
Go up one level in this thread
On September 09, 2002 at 17:52:45, Robert Hyatt wrote:
>On September 09, 2002 at 16:13:00, Gerd Isenberg wrote:
>
>>Hi all,
>>specially algorithm freaks,
>>
>>I'm currently looking for an efficient algorithm to determine whether two bits
>>in a bitboard are connected by "ones". Actually i use following recursive one,
>>but isn't there something smarter?
>>
>>
>>bool isConnected(BitBoard &theBB, int from, int to)
>>{
>> BitBoard adjacentBB = KingAttacks(from) & theBB;
>> theBB &= ~adjacentBB;
>> while (adjacentBB)
>> {
>> int sq = findLSBAndReset(adjacentBB);
>> if (sq == to) return true;
>> if ( isConnected(theBB, sq, to) ) return true;
>> }
>> return false;
>>}
>
>Precompute a table, char connected[64][64]. If square I and J are connected,
>for any value of I and J, set connected[I][J]=1, else set it to zero.
>
>Now you have a quick test.
>
>If you are wanting to see if a rook is connected to another rook, that is
>a different issue...
>
Thanks Bob,
Sounds great, have to think about...
But as far i IMHO believe to understand you have to reinitialize the whole array
if your position and the "allowed-set" changed . Isn't that too expensive, if
you only want to know on the fly whether the king on a1 may walk to b8?
Gerd
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