Scalable Search in Computer Chess: Algorithmic Enhancements and Experiments at High Search Dephts

279 Pages·2000·8.05 MB·English

by  Ernst A. Heinz (auth.)

Computational Intelligence
Series Editor:
Wolfgang Bibel · Rudolf Kruse · Bernhard Nebel
Ernst A. Heinz
Scalable Search in
Computer Chess
Algorithmic Enhancements and Experiments
at High Search Depths
Ernst A. Heinz
Scalable Search in
Computer Chess
Computational Intelligence
edited by Wolfgang Hillel and Rudolf Kruse
The books In.this series conthDute to the long-"r~nge goal pfumlerstanrung and rea
lizing intelligent behaviour in some envIronment. 'Thus t!;ley' covertopics from the
disCiplines ofArtificial1ntetl,genceandCogni!:tve Science, combined also caJled In- '
tellectics, as well as from fierds interdJsciplinarilyieJ:at'ed with these. Computati(}'
nallnteUigence cOmprises ba~ic k~Owledge as'wellas applications.
Das rechnende Gehlrn
by Patricia S. Church land 'lnd Terrence:r. Sejnows~i
Neuronale Netze und Fuzzy..systeme
by DetlefNauck,Frank Klawonn and Rudolf Kruse
Fuzzy-Clusteranalyse
by Frank Hoppner,. Frank KlaW\Jnn.and Rudol f Kruse
Elnfiihrung In Evolutloniire,Algorlthmen
by Volker Nissen
Neuronale Netze
by Andreas Scher.er
Sehen und die Verarbeltung~vl.ueller Informatlonen
by Hanspeter A. Mallo!
Betriebswlrtscbaftllche.Anwendungen des Soft Computing
by Biethabn et al. (Ed.)
Fuzzy Theorle und Stochastlk
by Rudolf Seising (Ed.)
MultiobJecflve Heuristic Search
by Pallab Dasgupta, P. P. Chakrabarti and S. C. DeSarkar
The Efflclence ofTheorem Proving Strategies
by David A. Plaisted an~ Yunshan Zhu
Scalable Search in Computer Chess
by Ernst A. Heinz
Among others the following books were published
in the series of ArtiRciallntelligence
Automated Theorem Proving
by Wolfgang Bibel (out of print)
Fuzzy Sets and Fuzzy Logic
Foundation of Application - from a Mathematical Point of View
by Siegfried Gottwald . .
Fuzzy Systems In Computer Science
edited by Rudolf Kruse, Jorg G'ebhard arid {{ainerPalm
Automatlsche Spracherkennung
by Ernst Gunter Sthukat-Talamazzinl ;
Deduktive Datenbanken
by Armin B. Cremers, UJrike Grielhahn and RaJf Hinze
Wissensreprasentation und Inferenz
l
by Wolfgang Bibel, Steffen Holldobler and Torsten ~Chaub .
Ernst A. Heinz
Scalable Search in
Computer Chess
Algorithmic Enhancements
and Experiments at High Search Dephts
I I
vleweg
Die Deutsche Bibliothek - CIP-Cataloguing-in-Publication-Data
A catalogue record for this publication is available from Die Deutsche Bibliothek
(http://www.ddb.de )
ISBN 978-3-528-05732-9 ISBN 978-3-322-90178-1 (eBook)
DOI 10.1007/978-3-322-90 I 78-I
Authors adress: [email protected]
1s l Edition 2000
All rights reserved
© Springer Fachmedien Wiesbaden 2000
Originally published by Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig/ Wiesbaden,in 2000.
No part of this publication may be reproduced, stored in a retrieval
system or transmitted, mechanical, photocopying or otherwise
without prior permission of the copyright holder.
Printed on aCid-free paper
v
Preface
This book presents the results of our past two-and-a-half years of research aimed
at increasing the scalability and performance of game-tree search in computer
chess. We elaborate on our respective works in the areas of (I) selective forward
pruning, (II) the efficient application of game-theoretical knowledge, and (III)
the behaviour of the search at increasing depths.
The broad range of topics covered by the three distinct parts of the book seek
to provide interesting material for everybody interested in the field of "Compu
tational Intelligence", regardless of their individual focus (researcher, student,
or other). The text does not require readers to know about chess and computer
game-playing beforehand. The initial chapter entitled "Computer-Chess Primer"
introduces all the necessary basics and fundamentals thereof.
The remaining chapters, however, go far beyond those topics. They show
how to make sophisticated game-tree searchers still more scalable at ever higher
depths. Throughout the whole book, our high-speed and master-strength chess
program DARKTHOUGHT serves as a realistic test vehicle to conduct numerous
experiments at unprecedented search depths. The extensive experimental evalu
ations provide convincing empirical evidence for the practical usefulness of the
techniques presented by us. These results will certainly be of special interest to
researchers and programmers of computer strategy-games alike (chess, checkers,
Go, and Othello in particular).
Last but not least, I like to mention that I am most grateful to the series
editors for offering me the opportunity to publish my book under their auspices.
Ernst A. Heinz - September 1999
VII
Thanks
• Prof. Dr. Walter F. Tichy remained committed to serve as my supervisor and
provided continued support even after I switched topics from parallel com
puting to computer chess in late 1996. From him I learned how to contribute
to science and how to embrace the scientific community.
• Prof. Dr. T. Anthony Marsland agreed to serve as my co-supervisor although
he hardly knew me at the time of my request. In the end, he even shortened
his personal holidays for the sake of letting me schedule my thesis defence
smoothly.
• Prof. Dr. Jaap van den Herik superbly edited my articles in the ICCA Jour
nal. Our most pleasant and constructive cooperation markedly improved the
quality of my writing.
• Markus M. Gille dedicated much of his spare time to improve the implemen
tation of our chess program DARKTHOUGHT.
• Pawel Lukowicz and I first met in October 1987, shortly before our first
term in Computer Science began at the University of Karlsruhe. We then
lived together in the same flat for 6 years, earned our M.Sc. degrees together
in early 1992, worked together in the same bureau for 7 years, and finally
finished our Ph.D. studies together in mid-1999. We always had fun together
and our fruitful discussions mostly clarified topics to the very last detail.
• My parents Jutta Heinz and Prof. Dr. Ernst Heinz shielded me against
hardship throughout my whole life.
• Marianne J. S. Hardt makes it all worthwhile. She cheered me up when I was
down although she had to endure my countless days of late-night work on
computer chess during the past years.
VIn
Acknowledgements
• A.s.E. GmbH loaned additional RAM for free during the 13th World Micro
computer-Chess Championship (October 1995) and a 433 MHz DEC Alpha-
21164a PC-l64 workstation for free during the 14th World Microcomputer
Chess Championship (October 1996).
• DELTA Computer Products GmbH loaned a 500 MHz Compaq Alpha-21264
XP-lOOO workstation with 1 GB SDRAM for free during the 9th World
Computer-Chess Championship (June 1999) and the 16th World Micro
computer-Chess Championship (June 1999) thanks to the courtesy of Heinz
Dieter Schutt, then Chief Marketing Officer of DELTA.
• Digital Equipment Corp. (DEC) paid for two 500 MHz DEC Alpha-21164a
PC-l64 workstations in March 1997 under external technology research con
tract DE-0032-97 entitled "Optimization and Fine-Tuning of a Sophisticated
Tree-Searching Application for 64-bit Alpha CPUs" as negotiated by the
courtesy of Dr. Frank Severin, then Head of Digital's External Technology
Group Europe.
• Digital Equipment Corp. 's Workstation Division (in close collaboration with
KryoTech Inc., see below) shipped a cooled 767 MHz Alpha-21164a Digital
Personal Workstation prototype with 512 MB SDRAM from the USA to
France and back for use by DARKTHOUGHT during the 15th World Micro
computer-Chess Championship (October 1997). Together with the prototype
they sent Jeff Forsythe over to Paris to attend the week-long championship
where he provided superb service to anybody who needed help. Furthermore,
Digital Equipment Corp. shipped an identically equipped 600 MHz Alpha-
21164a workstation from the USA to Germany for the final preparations of
our team. Digital Equipment Corp. did all of the above for free thanks to
the courtesy of Ron Locklin, then Vice President of Digital's World-Wide
Workstation Marketing Division.
• KryoTech Inc. (in close collaboration with Digital Equipment Corp., see
above) provided a cooled 767 MHz Alpha-21164a Digital Personal Worksta
tion prototype for use by DARKTHOUGHT during the 15th World Micro
computer-Chess Championship (October 1997) thanks to the courtesy and
greatly appreciated personal efforts of Rob diGiacomo, then Executive Vice
President and Chief Marketing Officer of KryoTech Inc.
Acknow ledgements IX
• Sun Microsystems Inc. donated a 167 MHz UltraSparc Creator workstation
for program development and 64-bit Sparc V9 benchmarking in February
1996 due to the courtesy of Eckhard Schaumann, then Head of Sun's German
University Cooperation Unit.
• The Gunther & Ingrid Schroff Foundation (administered by the Chancellor
of the University of Karlsruhe), the Karlsruher Hochschulvereinigung, and
the Institute for Program Structures and Data Organization (IPD, Chair
Prof. Tichy) awarded several generous travel grants on the occasions of tour
nament participations from the 8th World Computer-Chess Championship
(May 1995) onwards.
• The Institute for Program Structures and Data Organization (IPD, Chair
Prof. Tichy) at the University of Karlsruhe provided abundant computing
resources for our exclusive use throughout the whole work. Without these
plentiful resources our extensive experiments with DARKTHOUGHT would
have been impossible to undertake.
• The International Computer-Chess Association (ICCA) paid for our air
fares from Germany to Indonesia on the occasion of the 14th World Micro
computer-Chess Championship (October 1996).
• The editorial staff of the ICCA Journal provided outstanding cooperation
and superb editing of my published material.
• Peter W. Gillgasch, a former co-founder of IPD's computer chess group,
belonged to the DARKTHOUGHT team until April 1996. His various con
tributions are highly appreciated until today. As described in Section A.2
"Implementation History", DARKTHOUGHT still contains some source code
written by Peter.
• Andreas Junghanns from the University of Alberta (Canada) provided the
detailed self-play results of the game-playing programs CHINOOK, KEYANO,
PHOENIX, and THE TURK in electronic form.
XI
Contents
Summary and Contributions 1
0 Computer-Chess Primer 7
0.1 The Game of Chess. . · . 7
0.2 Basic Search Techniques · . 11
0.2.1 Minimax and N egamax 11
0.2.2 Alpha-Beta · .. 13
0.2.3 Minimal-Window Search . 16
0.2.4 Quiescence Search 17
0.3 Advanced Search Techniques 20
0.3.1 Search Extensions 20
0.3.2 Transposition Tables 22
0.3.3 Move Ordering 22
0.3.4 Iterative Deepening 23
0.3.5 Aspiration Search 24
0.3.6 Forward Pruning . 24
I Forward Pruning without Tears
1 Adaptive Null-Move Pruning 29
1.1 Introduction. · . · . 29
1.2 Related Work . · . · . 31
1.3 Standard Null-Move Pruning 32
1.4 Recursively Adaptive Null-Move Pruning 34
1.4.1 Theory 35
1.4.2 Practice · . 36
1.5 Conclusion · . · . · . 39
1.6 Appendix - Experimental Setup 40
2 Extended Futility Pruning 41
2.1 Introduction. . . · . 41
2.2 Normal Futility Pruning 42
2.2.1 Theory · . · . 42
2.2.2 Practice · . · . 44
2.3 Futility Pruning at Pre-Frontier Nodes 44
2.3.1 Theory 44
2.3.2 Practice 45