Author: Gerd Isenberg
Date: 12:12:17 09/21/02
Go up one level in this thread
On September 21, 2002 at 13:11:30, Sean Mintz wrote:
>Could your functions be placed in to some popular bitboard engines (perhaps
>Crafty or Beowulf?) so that we could measure their performance?
Should be possible, in principle. You need msc++ with processor pack installed
or intel c++.
You have to consider the mapping of squares to the bits of the bitboard,
But due to symmectric only the comments may be wrong (except pawns).
I'll try it with IsiChess, where i actually have prototypes like this:
BitBoard CNode::RookAttacks (UINT sq) const;
The three neccesary instructions that pass a bitboard to edx:eax specially the
two "movd reg32, mmx" are rather expensive due to amd vector path instructions
(70 secs indstead of the 57 secs in the loop, no idea with intel PIV).
But in the first step i will use them:
BitBoard CNode::RookAttacks (UINT sq) const
{
#ifdef USE_MMXFILL
__asm
{
movd mm2, [sq]
movq mm1, [one]
psllq mm1, mm2
mov ebx, [this]
movq mm6, [ebx].m_EmptySquares
... do the getRookAttacksMMX() code
movd eax, mm0 ; lowboard to eax
punpckhdq mm0, mm0 ; highboard to lowboard
movd edx, mm0 ; highboard to edx
}
#else
// none mmx code
#endif
}
special mmx-version should conditionally replace something like this:
BitBoard CNode::GetAttackedBy(UINT sq) const
{
return
(RookAttacks(sq) & RookMover())
| (BishopAttacks(sq) & BishopMover())
| (BPawnAttacks(sq) & GetWPawnBB())
| (WPawnAttacks(sq) & GetBPawnBB())
| (KnightAttacks(sq) & GetKnightBB())
| (KingAttacks(sq) & GetKingBB())
;
}
The next step might be to write some polymorphs which avoid the expensive
"movds". But that implies some rearrangement in the source code, which i like to
avoid. A better idea might be to wait for 64bit hammer and a (hopefully) fast
"movq reg64, mmxReg".
Final step might be to gain something from the (may be main) feature, getting
attacks for multiple pieces of one kind simultaniously. But thats requires
really source rearrangements.
To generate king moves, it's usefull to have a bitboard with all attacks from
all opposite colored pieces. This is quite easy to implement, with the same
effort than getting all pieces attacking one square. Instead of calling
"GetAttackedBy" for adjacent king squares, only call the new routine
"getAllAttacked(int side)" once.
I think in eval there is also some potential...
Looking for a set of squares "reachable" in two (ore more) moves might be an
interesing task here and there...
cheers,
Gerd
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