HIARCS Chess Software for PC Windows, Apple Mac and iPhone/iPad UCI Engine Options
World Championship winning computer chess software program & downloads for chess database, analysis & play on PC, Mac and iPhone


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HIARCS UCI 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!

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

Position Cache Options


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.

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.

Search and Playing Style

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.

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)

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

Hiarcs Draw Value (0)

This setting enables you to specify in centipawns if HIARCS should favour a draw or not. Positive numbers means HIARCS will prefer draws, negative it will try to avoid them. This is a dangerous option expecially in endgames. The default is 0 which neither likes or dislikes draws. Special note: The HIARCS style normally means it naturally avoids draws and plays actively.

Swindle (ON)

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 ON.

Opening Book Options

Own Book (ON)

This setting allows HIARCS to use its opening book. Hiarcs 10 UCI uses the
book named HBook10.hcs found in its folder. Hiarcs X50 UCI uses the book
named HBookX50.hcs found in its folder. Hiarcs UCI uses book learning.
The default is ON and is best.

PLEASE NOTE: You should turn the GUI book off or load an empty book so that
Hiarcs will be able to play from its own book. Otherwise the GUI will play
the book moves from another book and not ask the Hiarcs engine for a
move in the opening.

Book File

This option is not available on Hiarcs 10 UCI. On Hiarcs X50 UCI it enables the user to specify the name of the book used by Hiarcs X50. The book must reside
in the same folder as the engine.

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 Style (Tournament)

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

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.

Endgame Tablebase Options

Use Tablebases (ON)

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

Tablebase Depth (2)

This setting allows you to specify at what depth the tablebases will be accessed. Highly figures reduce tablebase access, lower figures increase tablebase access. The default is 2.

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.


Miscellaneous Options

UCI_LimitStrength (OFF)

This option when ON makes HIARCS weaken its play down to the Elo level setting
UCI_Elo. The default is naturally OFF.

UCI Elo (1925)

This enables you to select a limited strength HIARCS based on a specific Elo
rating. This option is only applicable if the UCI_LimitStrength option is set.

GUI Time Lag (OFF)

Some GUIs deduct from the engine clock the time the GUI consumes updating the display. This can mean that for each move the GUI takes 50 milliseconds or more extra time away from the engine leading to time trouble for the engine in that GUI. We noticed this in the Shredder UCI GUI. However, in the Chessbase Fritz and Arena GUIs we did not see any such problems. The default is OFF. It should be OFF for all Chessbase GUIs and Arena. When using HIARCS UCI in the Shredder UCI GUI it should be switched ON.

AutoSave PGN (ON)

This option when ON tells HIARCS to write each game it plays to an autosave.pgn
file in its folder. This can be a useful reference of the games played.
The default is ON.

Licensed To

This read only string gives the name the HIARCS product is licensed to.

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"generally I use HIARCS." - Five time World Chess Champion Vishy Anand, in a recent interview when asked what chess program he uses to analyse with
"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 & 2012 world title matches

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

Highest performance reached depends on computer used. Computer Chess Software with world class chess engine playing strength.
HIARCS is designed and developed by Mark Uniacke in England.

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