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HIARCS 11 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 11.2 UCI chess engine and a description of their affect on the engine. Any defaults are in parentheses and explained in the text.


Multiprocessor Options

Core Threads (Default Max CPUs <= 8)

This option is only available in the Multiprocessing version of HIARCS UCI. It allows you to configure the number of threads the HIARCS chess engine will use during its thinking. The default is to utilise as many CPUs as available up to a maximum of 8. We hope to raise this limit when we have verified the program on more CPUs. If you wish for example to run HIARCS 11 MP UCI on only one processor you can set this value to 1.


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 2048Mb 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 or analyses. 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 default and probably the best setting for this parameter is 10, but some of our test team still prefer fp=11.

Threat Depth (5)

Using this setting you can determine how deep HIARCS examines threats. The default is 5 and we believe this may be the best setting. Previously Hiarcs 11 used a threat depth of 3.

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 (ON)

This setting make HIARCS play in a more Hyper-Modern style. The default is ON. This setting in the past has sometimes been shown to increase the strength of HIARCS. Previously HIARCS 11 had this option 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 own engine opening book. Hiarcs 11 UCI uses the book named H11Book.hcs found in its folder.  Hiarcs UCI uses book learning. The default is ON when HIARCS can find its opening book and is the best option.

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 Status

This option option string is read only and tells you if the book loaded ok or not. You will get a warning if the opening book is read-only as that means book learning cannot operate. If Hiarcs cannot load or read the book you will get an error here.

Book File

This option enables the user to specify the name of the book used by HIARCS. 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 tournament book has about 690,000+ positions. Please use the Tournament book for serious chess play.

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. Higher 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_Chess960 (OFF)

This option when ON makes HIARCS play Fischer Random Chess or Chess960 as it is perhaps better known. The default is naturally OFF.

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 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.

Verbose UCI (OFF)

Some GUIs seem to react very slowly to UCI output. This option when OFF reduces the amount of information which is output to the GUI and can make the GUI more responsive. We noticed when this option is ON the Chessbase GUIs become slower during engine use so we recommend this option is switched OFF especially in Chessbase GUIs. The Shredder UCI GUI is much better at handling verbose UCI output. The default is OFF.

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.

Registration Code

This read only string which is only visible when the engine is not registered gives the registration code you should email to so we can generate a license key for you to activate HIARCS.

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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

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