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HIARCS 10 Chess Engine Options

The HIARCS chess engine has many parameter options which can be modified to change the playing style and strength of the chess engine. We believe the default options were the best known at release but maybe you can find a better set of parameters!

Since release there has been evidence that the Hypermodern setting when switched on improves Hiarcs 10 by about 10 Elo.

Below you will find the options available in the HIARCS 10 chess engine and a description of their affect on the engine. Any defaults are in parentheses and explained in the text.


The hash table is typically large area of memory used by the HIARCS chess engine to record previous calculations to speed up future computations. This can be set from 1Mb to 1024Mb in 1Mb steps. You are recommended to use 50% of your machines physical RAM for Hash tables. Please check that your hash table size setting does not cause disk activity. If so HIARCS will run significantly slower - in this case please decrease the hash table size and try again.

Clear Hash

This allows you to clear the hash table of its information. This option does not normally need to be used.

Retain Hash (ON)

This option enables HIARCS to maintain its hash table between moves and this improves its play as well as its learning ability and analysis. The default is ON.

Playing Style (Normal)

HIARCS has three different playing styles, namely, Normal, Aggressive and Solid. The Normal style is the default and believed to be best.

Smart Search (ON)

This setting allows HIARCS to apply some smartness to its search selections. The default is ON and this is the best setting.

Selectivity (7)

The HIARCS search is selective - it tries to cut out irrelevant moves and variations. You can set the selectivity from 0 (no selectivity) to 7 (very selective). The default and strongest setting is 7.

Futility (ON)

This setting when ON allows Hiarcs to discard moves and variations which appear to be futile. This enables a slightly deeper search at the cost of a very small risk of overlooking something. Overall it appears to be a gain so the default is ON.

Steady Search (OFF)

This setting tells Hiarcs to keep its search steady and regular through its progressive deepening of search. At present this option has the default OFF as it appears this is slightly the stronger setting.

Forward Pruning (10)

This setting determines how aggressive Hiarcs 10 prunes the search tree to discard unnecessary variations and moves. The best setting and default for this parameter is 10.

Threat Depth (3)

Using this setting you can determine how deep HIARCS examines threats. The default is 3 and we believe this may be the best setting.

Swindle (OFF)

In positions which are normally drawn (for example K+R v K+B), the swindle setting tells HIARCS to keep pressing for the win if it is the stronger side. This is most applicable against human opponents. Default is OFF as a courtesy.

Own Book (ON)

This setting allows HIARCS to use its opening books. It uses the book named OBook.hcs found in the HIARCS folder. There are a variety of books available on www.hiarcs.com which can be copied into the HIARCS folder and used. The default is ON and is best.

Book Style (Tournament)

This setting allows you to choose the style of the opening book from Wild, Wide, Normal and Tournament. Please use the default "Tournament" for serious chess.

Book Positions

This setting informs you of the number of positions in the book which is loaded. The small book as about 37,000 position, the tournament book has 300,000+ positions. Read the readme.txt inside each book download for instructions. Please use the Tournament book for serious chess play - available for free download from www.hiarcs.com.

Book Learning (ON)

This setting allows HIARCS to use its experiences with the current book to make decisions about which moves to make from the book. The default is ON.

Position Learning (ON)

This setting allows HIARCS to learn from the games it plays. This can improve its play in future games. The default is ON.

Combinations (OFF)

This setting makes HIARCS look deeply at tactical combinations. This setting can help HIARCS find combinations sooner but at the cost of making the overall search less deep. When ON, this setting usually results in weaker play. The default is OFF.

Hyper-Modern Play (OFF - it now seems ON is an improvement)

This setting make HIARCS play in a more Hyper-Modern style. The default is OFF.

Use Tablebases (ON)

This setting allows you to turn access to Nalimov endgame tablebases ON or OFF. The default is ON.

Nalimov Cache

This sets the amount of memory used to cache endgame tablebases. This value should be about 1/8th of the hash table setting for optimum performance.

Nalimov Path

The is the location of your endgame tablebases.


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"It is exhilarating to play [HIARCS], more, a lot more than with any other strong program. It is a real pleasure to be defeated that way. Fast, lightning, unexpected death." - Fernando Villegas, April 2007
"HIARCS is much better positionally than Deep Blue." - Garry Kasparov 1997 (after game 5 of the rematch)

World Chess Champion, Vishy Anand, used "Powerful" HIARCS machine in preparations for his 2010 world title match with Super GM Veselin Topalov

"This level of service is one other big reason to buy HIARCS." - John Jackson, November 2009

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HIARCS Chess Software is designed and developed by Mark Uniacke in England.
HIARCS is a trademark of Applied Computer Concepts Ltd. All other product trademarks acknowledged.
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