Pepito

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Pepito,

a Chess Engine Communication Protocol and UCI compliant open source chess engine written by Carlos del Cacho in C, first released in September 2000 [1]. The recent version comes with an own GUI written in C++ using wxWidgets and can create opening book databases from a pile of thousands of chess games, applying advanced data structures such as B-trees and skip lists [2]. As bitboard engine, Pepito applies rotated bitboards with 1/2 MiB lookup tables, indexed by the full 8-bit line occupancy, to determine sliding piece attacks. Pepito played the CCT4, CCT5 and CCT6 tournaments.

Features#

• NegaScout search algorithm
• Extensions to avoid horizon effect (i.e. check, recapture, pawn push, …)
• Transposition tables, pawn hash tables and evaluation cache
• AEL-pruning à la Heinz
• Static exchange evaluator, used for move ordering and also to cull losing captures in the quiescence search
• Lazy evaluation
• Nalimov Tablebases
• Pondering
• Book learning

Acknowledgments#

Pepito wouldn’t have come to life without the help from these guys, acknowledged by Carlos del Cacho in thanx.txt, shipped with the source files [4]:

• Bob Hyatt ( Crafty)
• Dušan Dobeš ( Phalanx)
• Daniel Homan ( EXchess)
• Adrien Regimbald ( Faile)
• Jon Dart ( Arasan)
• Andrew Tridgell & Jonathan Baxter ( KnightCap)
• Stuart Cracraft & Chua Kong Sian ( GNU Chess 5)
• John Stanback ( GNU Chess 4)

… further …

• Eugene Nalimov for his Endgame Tablebases

… and

• Jonathan Schaeffer
• Alexander Reinefeld
• Ernst A. Heinz
• Aske Plaat

for their papers, and

• Bruce Moreland
• Dieter Bürßner
• Brian Richardson
• Tony Werten

and many others at CCC for their help…

Selected Games#

CCT4, round 2, Pepito - Yace [5]

[Event "CCT4"]
[Site "Internet Chess Club"]
[Date "2002.01.19"]
[Round "2"]
[White "Pepito"]
[Black "Yace"]
[Result "1/2-1/2"]

1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Be3 e6 7.f3 b5 8.g4 h6 
9.Qd2 Nbd7 10.O-O-O Bb7 11.h4 b4 12.Na4 Qa5 13.b3 Nc5 14.a3 Rc8 15.Qxb4 
Qc7 16.Nxc5 dxc5 17.Qa4+ Nd7 18.Ne2 c4 19.b4 Bc6 20.Qxa6 Ra8 21.Qxc4 Rxa3 
22.Bf4 Qb7 23.c3 Bb5 24.Qd4 Ra2 25.Kb1 Rxe2 26.Rh3 e5 27.Bxe5 Bc5 28.Qd5 
Bc6 29.Qc4 Bb5 30.Qd5 Bc6 31.Qc4 Bb5 32.Qd5 1/2-1/2

Clones#

The program Siboney by Francisco Rivera published in 2002 was based on Pepito with a changed evaluation [6] [7] [8]. In 2003, Deep<9> by pretended author Denis Grafen was proven a blatant clone of Pepito [9] [10] [11].

Forum Posts#

2000#

• New winboard engine released! by Carlos del Cacho, CCC, September 18, 2000
• Pepito 1.01 uploaded! Bugfix + adjustable hash size by Carlos del Cacho, CCC, September 20, 2000
• About Pepito and Amyan by José Carlos, CCC, September 24, 2000 » Amyan
• Pepito 1.03 available (Move now support & José C. bug fixed) by Carlos del Cacho, CCC, September 25, 2000
• Pepito v1.10 available w source by Carlos del Cacho, CCC, December 22, 2000

2001#

• Pepito 1.40 MMX LCT2 test by Gabor Szots, Winboard Forum, October 02, 2001 » LCT II
• Pepito 1.42 MMX build by Dann Corbit, Winboard Forum, October 04, 2001

2002#

• The New Pepito… by Dann Corbit, Winboard Forum, June 24, 2002
• new Pepito version available for download by Carlos del Cacho, Winboard Forum, July 27, 2002
• Config.dat for Pepito by Carlos Pesce, Winboard Forum, July 30, 2002
• New format of Config.dat for Pepito (built from the readme!) by Günther Simon, Winboard Forum, July 30, 2002
• Pepito 1.55 ( Read for fixes) by Nolan Denson, CCC, July 31, 2002
• Siboney = a Pepito clone ?? by Brice Boissel, Winboard Forum, August 06, 2002 [12]
• Pepito 1.54 and learning by Igor Korshunov, Winboard Forum, November 12, 2002

2003#

• Deep<9> Is a Clone based of Pepito? Really? by Volker Richey, CCC, March 13, 2003
• Deep9, Pepito and Leo’s Qualify by Matthias Gemuh, Winboard Forum, March 13, 2003

2004 …#

• Pepito @ CCT6 After thoughts by Nolan Denson, CCC, February 01, 2004
• Pepito problem by Tord Romstad, Winboard Forum, March 10, 2004
• Pepito 1.59 Windows 64-bit build available by Jim Ablett, CCC, December 20, 2007

External Links#

Chess Engine#

• Pepito Chess engine on Behance
• Pepito… that other xboard chess engine hosted by Thomas Mayer
• Index of /chess/engines/Norbert’s collection/Pepito (Compilation) by Norbert Raimund Leisner, hosted by Kirill Kryukov
• Pepito in CCRL 40/15

Misc#

• Pepito (disambiguation) from Wikipedia
• Pepito (sandwich) from Wikipedia
• Pepe (disambiguation) from Wikipedia
• Pepito (comics) from Wikipedia

References#

1. ↑ New winboard engine released! by Carlos del Cacho, CCC, September 18, 2000
2. ↑ Pepito Chess engine on Behance
3. ↑ Pepito Chess engine on Behance
4. ↑ thanx.txt
5. ↑ CCT4 - PGN-Download hosted by Volker Richey
6. ↑ Siboney is at the moment not available! by Frank Quisinsky, Winboard Forum, May 24, 2002
7. ↑ What is the state of Siboney now? by Günther Simon, Winboard Forum, June 26, 2002
8. ↑ Siboney = a Pepito clone ?? by Brice Boissel, Winboard Forum, August 06, 2002
9. ↑ Re: A Deep question by Carlos del Cacho, Winboard Forum, March 05, 2003
10. ↑ The truth about Deep <9> by Thomas Mayer, CCC, March 14, 2003
11. ↑ Information by Denis Grafen, CCC, March 15, 2003
12. ↑ What is the state of Siboney now? by Günther Simon, Winboard Forum, June 26, 2002

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