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 ¹, 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 ² to determine sliding piece attacks. Its static exchange evaluation considers alpha and beta ³. Evaluation features were tuned automaticly performing a Genetic algorithm ⁴.

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 ⁵.

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 ⁶ 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 ⁷

• 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