ChessGenius is the name of a chess-playing computer program written by Richard Lang who has in the past written programs that have won the World Computer Chess Championship on 10 occasions. It is a continuation of a series of programs (which included various incarnations of the Mephisto program) written by Richard Lang which won the World Microcomputer Chess Championship in 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991 and 1993. ChessGenius was the first computer to beat a world champion (Garry Kasparov) at a non-blitz time limit. This victory was particularly significant because in contrast to the victory two years later by Deep Blue which was running on very fast custom-built hardware, ChessGenius was running on only an early Pentium PC.
As well as playing chess, ChessGenius can read games created in .cbf (Chess Base Format) and .pgn (Portable Game Notation) formats and can analyse games assessing the moves played against its own evaluations. It is also possible to run other chess engines in the ChessGenius interface. The built-in opening book for ChessGenius for Windows was written by a team led by Ossi Weiner.
In the early 1990s ChessGenius was 'one of the first master-strength programs'. In an article comparing ChessGenius with Fritz in February 1994 Grandmaster and computer chess expert John Nunn wrote, 'My own opinion is that if raw playing strength is your dominant criterion, then go for Genius'. Its playing style has been compared to that of a 'micro-Karpov'. ChessGenius, like many of Lang's programs, was famous for having an 'asymmetric evaluation function' which means that moves and sequences of moves might be scored differently depending on whether they are to be made by the program or by the opponent (which has implications for which lines are 'forward pruned' in its calculations). For example, ChessGenius might give a low score to a wild attack of its own and so not calculate it and so not initiate it, but a high score to a wild attack by the opponent and so spend time calculating the implications of such an attack by the opponent, thus making its style of play very 'safe'. At the Intel World Chess Grand Prix in London in 1994 ChessGenius achieved a rating performance for the tournament of 2795 Elo rating. From 1994 until 1998 ChessGenius remained one of the top chess programs available. In 1999 ChessGenius dropped out of the top ten on the SSDF (Swedish Chess Computer Association) rating list and it continued to slip down the list over the following decade. The programmer Richard Lang has suggested that this was because the program does not scale well to faster hardware. Portable versions (for example for Palm and the original iPhone) perform exceptionally well because ChessGenius is particularly strong in weak hardware environments. Unlike most other commercial vendors, Richard Lang explicitly forbids including the PC version of ChessGenius in chess engine rating lists, so it is difficult to gauge its strength compared to other modern programs. It has been suggested that the reason the current PC version of ChessGenius (7.2) is marketed as 'Classic' is because it was the first ever platform for Genius engine to appear for, to distinguish it from the other versions primarily for handheld devices and not because apart from speed and efficiency enhancements, and updates to its openings book, the program has not changed dramatically since 1995.
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