Author: Sune Fischer
Date: 08:14:36 09/15/01
Hi
When I discovered that Crafty had some neat assembler rutines, I decided to test
if they where faster than my humble rutines.
I have up until now used a "raytracing" or boardtracing rutine to find the legal
moves for the sliding pieces. And for the knights, pawns and king I simply check
if the board has an allied piece on that square.
It's a simple way of generating the legal moves.
I still generate the attack bitboards to get the legal king moves though.
I then tried to find all the moves directly from the bitboards by using one of
Crafty's assember functions.
This part of my program is only a minor part, but none the less it runs a full 8
percent slower than my previous raytracing algorithm!!
This is what I have now:
void FindMovesQueen(..loads of pointers...)
{
int to_square;
BITBOARD bb=(~allied.occupied) & allied.attack[board.id[from_square]];
while (bb)
{
to_square=63-FirstOne(bb); // get a bit
bb ^= mask[to_square]; // remove the bit
movelist[++counter].from=from_square;
movelist[counter].to=to_square;
movelist[counter].piece=QUEEN;
movelist[counter].capturedpiece=enemy.piece[board.id[to_square]];
}
return;
}
(movelist, counter, from_square etc. are passed in the argument)
I know why it is slow too.
First I have to form the bb, that's 2 bitboard operations.
Then I need to run an algorithm, FirstOne from crafty, to find the first bit.
Then I need to mask out that found bit.
Both of these run several time pending on the while loop.
Next is 4 lines I always have, no matter how I do it, so we can safely ignore
those.
The while loop is a conditional much like the if's I use when raytracing, so
probably the if's and while almost cancel out.
All in all I have added a lot of operations to my program, I am not surprized it
is a lot slower. Given that the entire program suffer a slowdown by about 8.1
percent, I estimate that this technique is more than twice as slow as the
raytracing.
The upside of things is that I reduce my code by about 1000 lines or so, but is
this worth 8 percent in speed?
I know the use of 64 bit processors will give a nice boost to this method and I
probably can't expect anything like that for my tracing function, but frankly
I'm not sure it would be enough to catch up.
Am I mistaken, are the big boys doing something else?
Is there an even faster way?
I need to know :D :D
Thanks,
Sune
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