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Home * Engines * Ulysses

Ulysses [1]

a chess program by Ulf Lorenz and Valentin Rottmann. Ulysses used the unique approach of Controlled Conspiracy Number Search, developed and implemented by Ulf and Valentin within the research group of Burkhard Monien from the Paderborn University. Ulysses played the WCCC 1992 in Madrid, the WMCCC 1993 in Munich and the WCCC 1995 in Hong Kong as well the four early IPCCCs from 1991 until 1994, and was superseded by its successor P.ConNerS performing Parallel Controlled Conspiracy Number Search [2].


given in 1995 from the ICGA-site [3]:

Ulysses was the legendary conqueror of Troy and on his adventurous journey home to Athens he made many wanderings. The program 'UlyssesCCN' is written in C and uses a new searching technique called 'Controlled Conspiracy Number Search' (CCNS). The CCNS algorithm has been developed by Lorenz and Rottmann in their master thesis. CCNS takes up the Conspiracy Number scheme which was published by McAllester in 1988.
This scheme makes it possible to achieve selectivity in the plain search algorithm without any domain dependent (i.e. chess specific) knowledge. The search tree has to be kept in memory (at least implicitly). Conspiracy Numbers were further investigated by Schaeffer in 1989. He has implemented a Conspiracy Number Search (CNS) in his program 'Conspire', which showed good tactical performance but unfortunately not good positional play. In developing the CCNS we explicitly used, for the first time, the observed locality of other CNS algorithms. In the evaluation of leaf-nodes a CCNS algorithm is able to use quiescence searches with initial windows. Positional play becomes possible. UlyssesCNN also uses a hash table which recognizes transpositions. Last, but not least, only a best move is computed and no resources are wasted for computing an upper bound for the value of this move. All chess specific knowledge used is encoded in the evaluation function. This consists of a static evaluator and a small quiescence search. Using a Sparc 10 60MHz, UlyssesCCN searches about 8000 nodes per second, about 350 of them are Conspiracy Number nodes. The opening book consists of 11,000 positions. After 300 seconds at each position, Ulysses solves 281 positions of WinAtChess test set, consisting of 300 positions. To our knowledge, UlyssesCCN is the first chess program based on Conspiracy Numbers which achieved an acceptable result in a computer chess tournament. 

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Chess Program



  1. Head of Odysseus from a sculptural group representing Odysseus blinding Polyphemus. Marble, Greek, probably 1st century AD. From the villa of Tiberius at Sperlonga, Museo Archeologico Nazionale in Sperlonga, Odysseus from Wikipedia
  2. Ulf Lorenz, Valentin Rottmann (1996). Parallel Controlled Conspiracy-Number Search. Advances in Computer Chess 8
  3. Ulysses' ICGA Tournaments
  4. Bootleg Series #12: Cream – Winterland, San Francisco, CA. 10th March 1968 by Tom Caswell, February 25, 2015

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