OBender

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Monument of Ostap Bender 1 Monument of Ostap Bender ¹

Monument of Ostap Bender in Melitopol, Ukraine, Photo by Олег Довгаль, October 4, 2012, CC BY-SA 3.0, Wikimedia Commons, Остап Бендер — Википедия ↩︎

OBender, (previously called Qchess and Chess)
a Chess Engine Communication Protocol compliant open source chess program by Evgeniy Korniloff, written in C, with recent modifications by Serg Nifont. Sources of various versions are hosted by Jim Ablett ¹ ². Despite released more recently, OBender aka Qchess seems to be the oldest Russian WinBoard engine. QChess was a demonstration program of selective search as an example in Evgeniy Korniloff's book Программирование шахмат и других логических игр (Programming Chess and other logical games) ³. The program has an own graphical user interface, but can also play via WinBoard. A newer version of the engine was called Chess, applying a deeper but narrower selective search with an extended positional evaluation, until it evolved to OBender with an additional side branch called Woodpecker ⁴.

Contents

Description

OBender represents the board with 8x8 arrays and piece-lists, and applies negamax PVS with null move pruning, mate threat extensions, check extensions, LMR and quiescence search inside the iterative deepening framework. Beside the transposition table and a tree structure of principal variations, OBender features a persistent learn file and various personalities. Move ordering is further enhanced by the killer heuristic and history heuristic, and the evaluation takes material, piece squares, pawn structure, king safety, and mobility into account, also considering attacks and x-ray attacks and pinned pieces ⁵.

Etymology

OBender is named after the main character of the classic satirical novel The Twelve Chairs by the Odessan Soviet authors Ilf and Petrov, released in 1928, and its 1931 sequel The Little Golden Calf. “Smooth operator” and conman Ostap Bender is a tricky individual who makes people believe he's a chess grandmaster and makes a now very well-known speech about making a small town called Vasiuki very famous by engaging it into a series of chess matches against the whole world, and even against other planets ⁶ ⁷ ⁸.