Author: Uri Blass
Date: 05:11:41 12/20/02
Go up one level in this thread
On December 20, 2002 at 08:00:31, Gerd Isenberg wrote:
>On December 20, 2002 at 07:26:12, Sune Fischer wrote:
>
>>On December 20, 2002 at 06:40:45, Gerd Isenberg wrote:
>>
>>>>Hi Uri,
>>>>
>>>>but a pseudo legal move generator is faster. You have to check if the king is in
>>>>check only if you must evaluate a position.
>>>>What is the advantage of a slower legal move generator?
>>>>
>>>>Andreas
>>>
>>>Hi Andreas,
>>>
>>>Not sure about that. Detecting pinned pieces is a rather fast and loopless task
>>>with bitboards, specially with mmx-fill routines (unrolled for each of eight
>>>directions). In the same run one could also detect possible covered checkers fo
>>>the opposite side.
>>>
>>>eg. for one direction:
>>>
>>>// rooks or queens
>>>if ( enemyRookMover & allRaysFromSquare[ownKingSquare])
>>>{ // scan four staight directions
>>> dirBB = getLeftAttacks(ownKingBB) & getRightAttacks(enemyRookMover);
>>> pinned |= dirBB & ownPieces;
>>> covered |= dirBB & enemyPieces;
>>> ...
>>>}
>>>
>>>Of course it's a bit overhead but the gained information is also usefull for
>>>other things, as Uri already pointed out.
>>>
>>>If there are pinned pieces, one safes making/unmaking invalid moves and there is
>>>no need (may be only for debug purposes) to look whether a king may be captured.
>>>
>>>Gerd
>>
>>The overhead of making/unmaking pinned pieces is extremely small.
>>I count about 0.5-1.5% pinns, the make/unmake move rutines take maybe 20% (in my
>>case) but I only need to do half a move to see if the move is legal, in total
>>that's about 0.075% overhead because of illegal pinned moves!!
>>
>>I'm pretty sure there is _no way_ you can detect pinns faster and improve on
>>this overhead.
>
>Hi Sune,
>
>I'm not sure, specially if we consider hammer or SSE2. I use dumb6fill for 2 or
>3 directions simultaniously (8 mmx-registers). With SSE2 or hammer it can be
>done for all 8-directions in parallel, with sliders and king in one 128-bit-xmm
>register.
Hi Gerd,
I admit that I do not understand.
hammer,SSE2,dumb6fill?
I also did not understand the code that you wrote in previous post and I post
again in the end of this post but I guess that I need to change my all move
generator to use it(something that I do not plan to do in the near future) so
maybe it is better if I start to use bitboard only for pawn structure because I
could understand better there and it seems that I do not need to change all my
data structure to use it.
Uri
N.B:the relevant code that I did not understand:
eg. for one direction:
// rooks or queens
if ( enemyRookMover & allRaysFromSquare[ownKingSquare])
{ // scan four staight directions
dirBB = getLeftAttacks(ownKingBB) & getRightAttacks(enemyRookMover);
pinned |= dirBB & ownPieces;
covered |= dirBB & enemyPieces;
...
}
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