Onno

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Onno, was a commercial chess engine developed by Onno Garms, written in C++ and released in May 2009. After announcing the end of Onno's development in March 2011, Onno Garms revealed several ideas that made Onno stronger. The 32/64-bit Windows or 64-bit Linux executables communicate with a chess GUI via UCI.

=Description=

Basics
Onno uses a fixed shift variation of Magic bitboards to determine sliding piece attacks. Its static exchange evaluation considers alpha and beta. Evaluation features were tuned automaticly performing a Genetic algorithm.

Search
Onno applies an iterative search along with PVS, null move pruning and verification search. Onno further uses a technique dubbed bad pruning similar to razoring. The idea is to apply a reduced search with a reduced window - if the search at depth d-3 says that one loses more then a pawn, it does not search the move with the current depth d.

Parallel Search
The MP version of Onno searches in parallel utilizing YBWC by following Rainer Feldmann's 1993 Ph.D. thesis Game Tree Search on Massively Parallel Systems using virtual messaging.

Node Types
Onno determines expected Node Types to perform IID not only at PV-nodes but also at expected Cut-nodes. Onno Garms gave following rules
 * The root node is a PV-node.
 * The first child of a PV-node is a PV-node
 * The further children are searched by a scout search as CUT-nodes
 * PVS re-search is done as PV-node
 * The first node of bad pruning is a CUT-node
 * The node after a null move is a CUT-node
 * The first node of null move verification is a CUT-node
 * Internal iterative deepening does not change the node type
 * The first child of a CUT-node is an ALL-node
 * Further children of a CUT-node are CUT-nodes
 * Children of ALL-nodes are CUT-nodes

=See also=
 * Iterative Search in Onno

=Forum Posts=

2009

 * Magic with fixed shift by Onno Garms, Winboard Forum, March 18, 2009
 * Onno 0.12 by Ted Summers, CCC, April 04, 2009
 * New commercial engine soon: Onno by Jouni Uski, CCC, May 17, 2009
 * Onno 1.0 is now available by Graham Banks, CCC, May 30, 2009
 * About becoming Commercial. The Onno Case by Fernando Villegas, CCC, June 02, 2009
 * Onno 1-1-1 released by Eduard Nemeth, CCC, August 30, 2009

2010

 * Onno MP beta has been released to customers by Martin Thoresen, CCC, February 27, 2010
 * Re: DTS Structure by Onno Garms, CCC, May 28, 2010 » Iterative Search in Onno

2011 ...

 * Development of Onno ends by Onno Garms, CCC, March 13, 2011
 * Root node search by Onno Garms, CCC, March 13, 2011 » Root
 * Software Engineering by Onno Garms, CCC, March 13, 2011 » History Heuristic, Toga
 * Bad Pruning by Onno Garms, CCC, March 13, 2011 » Pruning
 * On internal iterative deepening by Onno Garms, CCC, March 13, 2011 » Internal Iterative Deepening, Node Types
 * Less null move pruning by trans map by Onno Garms, CCC, March 13, 2011 » Null Move Pruning
 * Playing better moves in drawish positions (anti-0.00) by Onno Garms, CCC, March 13, 2011 » Draw, Contempt Factor
 * On parallelization by Onno Garms, CCC, March 13, 2011 » Parallel Search
 * Parameter tuning by Onno Garms, CCC, March 13, 2011 » Automated Tuning
 * Memory-PV-Search by Onno Garms, CCC, March 13, 2011 » Principal Variation Search
 * Move ordering by PST by Onno Garms, CCC, April 16, 2011 » Piece-Square Tables, History Heuristic, Move Ordering
 * SEE with alpha beta by Onno Garms, CCC, August 14, 2011 » Static Exchange Evaluation, SEE - The Swap Algorithm

=External Links=

Chess Engine

 * Onno Chess Software
 * Interview mit Onno Garms by Frank Quisinsky, Schachwelt, December 25, 2009 (German)

Misc

 * Onno from Wikipedia

=References= Up one level