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Subject: Re: mate threat extension/null move

Author: Don Beal

Date: 19:04:41 09/29/04

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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!

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