HIARCS Chess Software for PC Windows, Apple Mac and iPhone/iPad UCI Engine Options
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HIARCS 14 UCI Chess Engine Information

On this page you can find detailed information about the HIARCS chess engine parameters and HIARCS folders.

The HIARCS chess engine has many files and 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 there are some interesting possible improvements!

HIARCS 14 Engine Options

Below you will find the options available in the HIARCS 14 UCI chess engine and a description of their affect on the engine. Any defaults are in parentheses and explained in the text.

Multi-core/processor Options

Threads (Default Max CPUs <= 16)

This option is only available in the Multiprocessing version of HIARCS (Deep HIARCS). 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 16. We hope to raise this limit when we have verified the program on more CPUs. If you wish for example to run HIARCS 14 on only one processor you can set this value to 1.
Default is the maximum CPU cores (<=16) in your machine.

Busy Threads (ON)

This option when set makes HIARCS utilise threads as always busy - that is to say they do not go to sleep when no work is available.
The default is ON.


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 (Active)

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

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 (extreme selective). The default and strongest setting is 7.

Optimistic Search (ON)

This setting tells HIARCS to search with a more optimistic view typically leading to deeper searching. In wild positions and tactical tests it may be found that an OFF setting is better. The default is ON.

Combinations (ON)

This setting makes HIARCS look deeply at tactical combinations. This setting can help HIARCS find combinations sooner. The default is ON.

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 Opponent (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 or computer opponents who do not use endgame tablebases. Default is ON.


Opening Book Options

Own Book (ON)

This setting allows HIARCS to use its own engine opening book. HIARCS 14 uses the book named Hiarcs14aBook.hcs located in the HIARCS data folder.  HIARCS 14 uses book learning. The default is ON and is clearly the best option.

Our tests have shown the own engine tournament book combined with the unique learning features are more than a match for any other commercial opening book we have played against.

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 the book name used and 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 Positions

This setting informs you of the number of positions in the book which is loaded. The tournament book has over 5 million 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, Surprise, Dynamic 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. HIARCS has clever book learning so please use it!  The default is ON and clearly best.


Endgame Tablebase Options

CPU Usage (100)

This parameter enables you to set the % of CPU that HIARCS will use. By default this is 100% for maximum strength. I have found it useful when using HIARCS for analysis under Chessbase GUIs on Windows Vista to set this to 98 or 99% so that the GUI is more responsive to user requests. In game or match play it should be set to 100%.

Use Tablebases (Normally)

This setting allows you to choose how often HIARCS accesses the Nalimov endgame tablebases. The available options are Often, Normally, Rarely and Never. The default is Normally.

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. Typically this is between 1Mb and 256Mb with 32Mb a commonly used amount with a 256Mb hash table.


Nalimov Path

The is the location of your endgame tablebases. HIARCS UCI can use up to 6 piece 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 (2330)

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 ON.

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 a 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.


This gives some brief information about HIARCS.



Important HIARCS folders

Mac OS X version

In your Documents folder you will find a HIARCS Chess folder with Books and EngineData folders. Please put new books in the Books folder. This only applies to HIARCS Chess Explorer & HIARCS 14 and later versions.

The earlier HIARCS chess engines and data files are both located in the same place on your hard disk.

The default location for all the files is:

/Applications/Sigma 6.2 HIARCS 13/HIARCS

PC Windows version

The HIARCS application holds files in the following locations:

Application Program folder

This is where the HIARCS application and readme text files are stored.
eg. "C:\Program Files\HIARCS Chess\HIARCS 14 WCSC"
Please note on x64 systems applications are stored in "Program Files (x86)".

Only the read-only files of the chess engine, bitmaps, license and readme text files are stored in the application folder.

Application Data folders

In your Documents folder you will find a HIARCS Chess folder with Books and EngineData folders. Please put new books in the Books folder. This only applies to HIARCS 14 and later.

Earlier HIARCS versions stored their important read/write data in the following app folder. It is located as follows:
eg. "C:\Users\<User Name>\AppData\Roaming\HIARCS Chess" - on MS Windows Vista or Windows 7
eg. "C:\Documents and Settings\<User Name>\Application Data\HIARCS Chess" - on MS Windows XP and earlier.

HIARCS installs and/or creates the following data files in the Application Data folder. These files are:
+ Hiarcs14aBook.hcs - Opening book for Hiarcs engines
+ Hiarcs14WCSC.lrn - Position Learning
+ H14WCSC.pgn - Autosave of games

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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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