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Created page with "'''Home * People * Guido Schimmels''' '''Guido Schimmels''',<br/> a German software developer contributing to FSF GNU and simil..."
'''[[Main Page|Home]] * [[People]] * Guido Schimmels'''
'''Guido Schimmels''',<br/>
a German software developer contributing to [[Free Software Foundation|FSF GNU]] and similar projects, such as [https://en.wikipedia.org/wiki/GNU_TeXmacs GNU TeXmacs] <ref>[http://www.texmacs.org/tmweb/manual/webman-about.en.html About TeXmacs (FSF GNU project)]</ref>, and the [https://en.wikipedia.org/wiki/ROX_Desktop ROX Desktop] <ref>[http://rox.sourceforge.net/desktop/node/270.html Tango Theme | ROX Desktop]</ref>.
He further is contributor of the [https://en.wikipedia.org/wiki/Ultimate%2B%2B Ultimate++] framework <ref>[http://www.ultimatepp.org/app$ide$About$en-us.html Copyright © 1999-2019 Ultimate++ team :: Ultimate++]</ref>.
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 [[Principal Variation Search|PVS]] vs. [[NegaScout]] <ref>[https://www.stmintz.com/ccc/index.php?id=20868 Re: Zero-width Window Null Move Search] by [[Guido Schimmels]], [[CCC]], June 18, 1998</ref>:
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 Instability|search anonomalies]]. If that happens NegaScout returns the value from the first search. That means you will have a crippled [[Principal Variation|PV]]. Then there is a refinement [[Alexander Reinefeld|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 [[Extensions|search extensions]]. NegaScout is slightly an [https://en.wikipedia.org/wiki/Ivory_Tower ivory tower] variant of PVS (IMHO).
==PVS==
<pre>
value = PVS(-(alpha+1),-alpha)
if(value > alpha && value < beta) {
value = PVS(-beta,-alpha);
}
</pre>
==NegaScout==
<pre>
value = NegaScout(-(alpha+1),-alpha)
if(value > alpha && value < beta && depth > 1) {
value2 = NegaScout(-beta,-value)
value = max(value,value2);
}
</pre>
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=19790 Re: Hash Table Size Versus Performance] by [[Guido Schimmels]], [[CCC]], June 02, 1998 » [[Transposition Table]]
* [https://www.stmintz.com/ccc/index.php?id=20057 Question to Bob: Crafty , Alpha and FindBit()] by [[Guido Schimmels]], [[CCC]], June 05, 1998 » [[Crafty]], [[BitScan]]
* [https://www.stmintz.com/ccc/index.php?id=20868 Re: Zero-width Window Null Move Search] by [[Guido Schimmels]], [[CCC]], June 18, 1998 » [[Principal Variation Search]], [[NegaScout]]
* [https://www.stmintz.com/ccc/index.php?id=23672 Failing low at the root] by [[Guido Schimmels]], [[CCC]], August 03, 1998 » [[Root]]
* [https://www.stmintz.com/ccc/index.php?id=25012 Books that help for evaluation] by [[Guido Schimmels]], [[CCC]], August 18, 1998 » [[Evaluation]]
* [https://groups.google.com/d/msg/alt.religion.kibology/vMQhc1hJc7Q/xpnuVGQYZa4J Re: Atheist IQ vs Theist IQ] by [[Guido Schimmels]], [https://groups.google.com/forum/?fromgroups=#!forum/alt.religion.kibology alt.religion.kibology], August 18, 1999
* [https://www.stmintz.com/ccc/index.php?id=230559 Re: GCC 3.1 fastest compiler at K7 !!] by [[Guido Schimmels]], [[CCC]], May 20, 2002
=References=
<references />
'''[[People|Up one level]]'''
[[Category:Programmer|Schimmels]]
'''Guido Schimmels''',<br/>
a German software developer contributing to [[Free Software Foundation|FSF GNU]] and similar projects, such as [https://en.wikipedia.org/wiki/GNU_TeXmacs GNU TeXmacs] <ref>[http://www.texmacs.org/tmweb/manual/webman-about.en.html About TeXmacs (FSF GNU project)]</ref>, and the [https://en.wikipedia.org/wiki/ROX_Desktop ROX Desktop] <ref>[http://rox.sourceforge.net/desktop/node/270.html Tango Theme | ROX Desktop]</ref>.
He further is contributor of the [https://en.wikipedia.org/wiki/Ultimate%2B%2B Ultimate++] framework <ref>[http://www.ultimatepp.org/app$ide$About$en-us.html Copyright © 1999-2019 Ultimate++ team :: Ultimate++]</ref>.
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 [[Principal Variation Search|PVS]] vs. [[NegaScout]] <ref>[https://www.stmintz.com/ccc/index.php?id=20868 Re: Zero-width Window Null Move Search] by [[Guido Schimmels]], [[CCC]], June 18, 1998</ref>:
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 Instability|search anonomalies]]. If that happens NegaScout returns the value from the first search. That means you will have a crippled [[Principal Variation|PV]]. Then there is a refinement [[Alexander Reinefeld|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 [[Extensions|search extensions]]. NegaScout is slightly an [https://en.wikipedia.org/wiki/Ivory_Tower ivory tower] variant of PVS (IMHO).
==PVS==
<pre>
value = PVS(-(alpha+1),-alpha)
if(value > alpha && value < beta) {
value = PVS(-beta,-alpha);
}
</pre>
==NegaScout==
<pre>
value = NegaScout(-(alpha+1),-alpha)
if(value > alpha && value < beta && depth > 1) {
value2 = NegaScout(-beta,-value)
value = max(value,value2);
}
</pre>
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=19790 Re: Hash Table Size Versus Performance] by [[Guido Schimmels]], [[CCC]], June 02, 1998 » [[Transposition Table]]
* [https://www.stmintz.com/ccc/index.php?id=20057 Question to Bob: Crafty , Alpha and FindBit()] by [[Guido Schimmels]], [[CCC]], June 05, 1998 » [[Crafty]], [[BitScan]]
* [https://www.stmintz.com/ccc/index.php?id=20868 Re: Zero-width Window Null Move Search] by [[Guido Schimmels]], [[CCC]], June 18, 1998 » [[Principal Variation Search]], [[NegaScout]]
* [https://www.stmintz.com/ccc/index.php?id=23672 Failing low at the root] by [[Guido Schimmels]], [[CCC]], August 03, 1998 » [[Root]]
* [https://www.stmintz.com/ccc/index.php?id=25012 Books that help for evaluation] by [[Guido Schimmels]], [[CCC]], August 18, 1998 » [[Evaluation]]
* [https://groups.google.com/d/msg/alt.religion.kibology/vMQhc1hJc7Q/xpnuVGQYZa4J Re: Atheist IQ vs Theist IQ] by [[Guido Schimmels]], [https://groups.google.com/forum/?fromgroups=#!forum/alt.religion.kibology alt.religion.kibology], August 18, 1999
* [https://www.stmintz.com/ccc/index.php?id=230559 Re: GCC 3.1 fastest compiler at K7 !!] by [[Guido Schimmels]], [[CCC]], May 20, 2002
=References=
<references />
'''[[People|Up one level]]'''
[[Category:Programmer|Schimmels]]
