Guido Schimmels

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Guido Schimmels, a German software developer contributing to FSF GNU and similar projects, such as GNU TeXmacs, and the ROX Desktop. He further is contributor of the Ultimate++ framework. In the late 90s and early 2000s, Guido Schimmels was engaged in computer chess programming, and made a couple of posts in CCC.

=PVS vs. NegaScout= Guido Schimmels in a CCC post on the difference of PVS vs. NegaScout : The difference is how they handle re-searches: PVS passes alpha/beta while NegaScout passes the value returned by the null window search instead of alpha. But then you can get a fail-low on the research due to search anonomalies. If that happens NegaScout returns the value from the first search. That means you will have a crippled PV. Then there is a refinement Reinefeld suggests which is to ommit the re-search at the last two plies (depth > 1) - but that won't work in a real program because of search extensions. NegaScout is slightly an ivory tower variant of PVS (IMHO).

PVS
value = PVS(-(alpha+1),-alpha) if(value > alpha && value < beta) { value = PVS(-beta,-alpha); }

NegaScout
value = NegaScout(-(alpha+1),-alpha) if(value > alpha && value < beta && depth > 1) { value2 = NegaScout(-beta,-value) value = max(value,value2); }

=Forum Posts=
 * Re: Hash Table Size Versus Performance by Guido Schimmels, CCC, June 02, 1998 » Transposition Table
 * Question to Bob: Crafty, Alpha and FindBit by Guido Schimmels, CCC, June 05, 1998 » Crafty, BitScan
 * Re: Zero-width Window Null Move Search by Guido Schimmels, CCC, June 18, 1998 » Principal Variation Search, NegaScout
 * Failing low at the root by Guido Schimmels, CCC, August 03, 1998 » Root
 * Books that help for evaluation by Guido Schimmels, CCC, August 18, 1998 » Evaluation
 * Re: Atheist IQ vs Theist IQ by Guido Schimmels, alt.religion.kibology, August 18, 1999
 * Re: GCC 3.1 fastest compiler at K7 !! by Guido Schimmels, CCC, May 20, 2002

=References= Up one level