Author: Stuart Cracraft
Date: 10:24:37 08/12/04
Go up one level in this thread
On August 12, 2004 at 10:42:20, Tony Werten wrote:
>On August 12, 2004 at 10:18:45, Stuart Cracraft wrote:
>
>>Here is the result of the 30 second per position test on 300 positions
>>using nothing, see>=0 to search a capture, see having to bring the score
>>within alpha and a margin (futility/delta), and with both.
>
>I'm not sure how it is usually done, but I don't think it is safe to prune the
>see score against alpha but rather the captured piece value. Else it makes your
>qsearch even more blind.
>
Hi Tony,
What I do is this:
quiesce
:
baseval = eval(bd);
:
while next capture move available; do
#define MARGIN 200 // 200 millipawns, 1000 = 1 pawn in my program
delta = MAX(alpha-MARGIN-baseval,0);
seeok=see(bd,qml[mvi].to);
if (seeok < delta || seeok < 0) { skip this capture move }
else {
make capture move
search capture move
unmake capture move
look for cutoff, etc.
}
endwhile
endquiesce
The part about the delta is the same as what GNU 5 presently does.
The other part of seeok < 0 is based on Bob
I am thinking that instead of using MARGIN of 200 I should just use
maxposnscore[sidetomove] since this is a dynamic maximum positional
score calculated for the side on move.
The above, separately and together, have been tested and do not provide
any huge improvement over using neither in a fixed time search. However,
in long fixed depth searches a 50% nodes reduction and 50% time reduction
has been seen.
Stuart
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