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Subject: Re: mate threat extension/null move

Author: Stuart Cracraft

Date: 09:43:48 10/01/04

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On September 29, 2004 at 22:04:41, Don Beal wrote:

>On September 29, 2004 at 10:23:20, Stuart Cracraft wrote:
>>For this one, I am *paying* $50 to the first person who can point out
>>the solution to make my mate threat work and make the Win at Chess #141
>>problem time drop from 95 seconds on a 1ghz p3 to ~30 seconds or less
>>on the same box.
>$50!  :-)  I'll have a go.
>In the code you posted,
>instead of:
>  if (!threat && donull && (material[stm^1]>weights[0][stm^1][rook])
>      && !checked && !inpv) {
>  if(!threat && donull && !checked) {
>and instead of:
>  if (value >= beta) {
>  if (value >= beta
>  && !inpv && (material[stm^1]>weights[0][stm^1][rook]) ) {
>The idea of these changes is to apply the null move search
>(and hence get the mate threat extension working) in the
>pv as well as other variations, while still preventing
>you pruning in the pv or believing in null move betas
>when material is too low.
>In the unlikely event that:
>(a) I have understood your code
>(b) I have correctly diagnosed a problem
>(c) my fix does not conflict with other things you do
>(d) it achieves your desired 3-fold speedup on 141
>then the $50 will be gratefully received, but don't
>send it to me - send it to the Steve Schwarz CCC
>donation fund!

Hi Don -- I remember reading your articles through the years
especially that one on null move. Thanks for your interest.

I did take your code and put it into my program and removed
both Ross Boyd's and Uri Blass's ideas to test. Since they had
already solved the problem of my slow WAC 141 from 95 down to
5 seconds but Bob now tells me it's no good since it throws
out the null move by disabling it for depth > 1 which is a
very bad idea. So I can't name Ross nor Uri as receivers of
the bet after all.

Since that is the case, the $50 bet is still open. I will
respect the wishes of donation of anyone winning the bet
if a "donatee" is named as you did.

Unfortunately, no one's code has yet won the bet but since it did
not worsen the program performance on my test suite, I have
kept yours in as permanent homage for the invention of null move!

As the bet is still open, other ideas are entertained. Full code
for entire program is available to well known people or people
with strong programs (same thing I guess!)


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