HIARCS 15 Engine series: UCI Chess Information

The HIARCS 15 series chess engines have many parameter options that can be modified to tailor the engine to your needs. We believe the default options were the best known at release but there are some interesting other possibilities for chess improvement.

HIARCS 15 Engine Options

Below you will find the options available in the HIARCS 15 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 Deep HIARCS (Premium and Deep editions). It allows you to configure the number of threads the HIARCS chess engine will use during its thinking. The default is set to 1/4 of the CPU unique threads available. This gives room to have multiple engines analysing at the same time without overusing the CPU resource. The maximum threads is 16 for the Deep edition and 32 for the Premium Deep edition. We hope to raise this limit when we have verified the program on more CPUs. If you wish for example to run HIARCS 15 on only one processor thread you can set this value to 1. Default is 1/4 of maximum CPU cores on your machine.

CPU Usage (100)

This option enables you to set the % of CPU that HIARCS will use. By default this is 100% for maximum strength. This option defaults to 100% and represents the engine running as fast as it can within the Threads setting. For example if Threads is set to 2 and CPU=100, HIARCS will try to utilise 2 threads on the CPU at 100%. We do not recommend changing this parameter as lowering the CPU value will weaken the engine. The default is ON.

Position Cache Options

Hash

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 16Mb to 4Gb (standard) and 32Gb for the Deep and Premium editions. The default is to use 256Mb. You are recommended to ensure that the total allocated hash tables for every running chess engine does not exceed 75% of your machines physical RAM or leave at least 2Gb of RAM free for other tasks. Please check that your hash table size setting does not cause disk activity. If so HIARCS (and your computer) 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=true)

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 and makes HIARCS play stronger.

Position Learning (ON=true)

This setting allows HIARCS to learn positions from the games it plays or analyses. This can improve the analysis and play, separate learned information is kept for Analysis and Play in the EngineData folder. The default is ON.

Search and Playing Style

Playing Style (Active)

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

Combinations (ON=true)

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

Use Null Move Pruining (ON=true)

This setting enables HIARCS to use Null move pruning, typically this is very effective and makes the search look deeper and more accurately. However, in some endings involving Zugzwang it can be benificial to switch off Null move pruning if Zugzwang is very likely. The default is ON.

Hiarcs Draw Value (0)

This setting is only applied when HIARCS is playing a game and it enables you to specify in centipawns if HIARCS should favour a draw or not when it is playing. Positive numbers means HIARCS will prefer draws, negative it will try to avoid them. This is a dangerous option especially 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.

White Draw Value (0)

This setting is only applied when HIARCS is analysing a game and it enables you to specify in centipawns if White favours a draw when playing. Positive values favour a draw for White, negative values favour a draw for Black. The default is 0 which neither likes or dislikes draws for either side. Special note: The HIARCS style normally means it naturally avoids draws and typically recommends active analysis.

Avoid Draw (OFF=false)

When this option is ON=true, HIARCS takes more risks to try to avoid draws. Since this can weaken the engine this option is OFF=false by default.

Detect Fortress (OFF=false)

In some positions one side who appears to be losing can produce a fortress position that the stronger side cannot break through thereby holding the draw. This type of position can be very difficult for computer chess engine to understand. This feature when set ON=true will enable HIARCS when analysing (not when playing) to look for fortress positions and detect them and give much more accurate evaluations in such positions.

Opening Book Options

Own Book (ON=true)

This setting allows HIARCS to use its own engine opening book. HIARCS 15 uses the book named Hiarcs15nBook.hcs located in the Books folder. HIARCS 15 uses book learning. The default is ON and is clearly the best option.

PLEASE NOTE: HIARCS can only use its own engine opening book if the chess GUI is not making book moves for the engine. HIARCS Chess Explorer allows you to select the engine opening book for HIARCS 15 engines to use. In other chess GUIs 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 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 in this setting.

Book Positions

This setting informs you of the number of positions in the book which is loaded. The engine book has over 14 million positions. Please use the engine book for serious chess play.

Book Mode (Tournament)

This setting allows you to choose the style of the opening book from Wild, Surprise, Dynamic and Tournament. The Tournament book plays the strongest lines. The Dynamic mode will provide more variation while still trying to stick to good lines. The Surprise mode tries to play surprising lines. The Wild mode has the most randomness and will often play extremely wild look opening lines. Please use the default "Tournament" for serious chess play.

Book Learning (ON=true)

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.

Limit Book Knowledge (OFF=false)

This setting when set to true will make HIARCS start forgetting its book knowledge when HIARCS is playing at reduced Elo levels. The weaker the Elo level the more limited the book knowledge will be! The default is OFF so HIARCS will use its book without limit on weaker Elo levels.

Endgame Tablebase Options

Nalimov Tablebases (ON=true)

This option when ON tells HIARCS to use Nalimov tablebases when they are available and a path to them is specified (see Nalimov Path for details).

Nalimov Probe Depth (1..15 default=6)

This setting determines down to what depth HIARCS will access the Nalimov endgame tablebases. Depth 1 is the deepest access since the depth value is reducing from the depth it is searching, e.g. when searching to a depth of 26 the depth counter starts at 26. The default is 6 and is a good compromise between too many Nalimov accesses from disk which lower values might produce and too few from higher depth values. If you find the nps rate of the engine is slowing down too much in endgames due to tablebase access (high tbshits and low nps rate) you could raise the depth value.

Nalimov Probe Limit (3..6 default=6)

This setting determines when Nalimov tablebases are accessed based on the number of pieces on the board, when there are less than the Probe Limit number of pieces HIARCS will try to access the Nalimov tablebases (subject to the other constraints like probe depth etc). The default is 6, and we do not recommend you change this value.

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 16Mb and 512Mb with 128Mb a commonly used amount with a 1024Mb hash table.

Nalimov Path

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

Syzygy Tablebases (ON=true)

This option when ON tells HIARCS to use Syzygy tablebases when they are available and a path to them is specified (see Syzygy Path for details).

Syzygy Probe Depth (1..15 default=2)

This setting determines down to what depth HIARCS will access the Syzygy endgame tablebases. Depth 1 is the deepest access since the depth value is reducing from the depth it is searching, e.g. when searching to a depth of 26 the depth counter starts at 26. The default is 2 and is a good compromise between too many Syzygy accesses from disk which lower values might produce and too few from higher depth values. If you find the nps rate of the engine is slowing down too much in endgames due to tablebase access (high tbshits and low nps rate) you could raise the depth value.

Syzygy Probe Limit (3..6 default=6)

This setting determines when Syzygy tablebases are accessed based on the number of pieces on the board, when there are less than the Syzygy Probe Limit number of pieces HIARCS will try to access the Syzygy tablebases (subject to the other constraints like probe depth etc). The default is 6, and we do not recommend you change this value.

Syzygy 50 Move Rule (ON=true)

This option determine whether the 50 move rule is observed for Syzygy wins or not. When set on wins that take longer than the 50 moves rule are not considered wins. The default is ON=true.

Miscellaneous Options

UCI_Chess960 (OFF=false)

This option when ON makes HIARCS play Fischer Random Chess or Chess960 as it is perhaps better known. The default is naturally OFF. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_LimitStrength (OFF=false)

This option when ON makes HIARCS weaken its play down to the Elo level setting UCI_Elo. The default is naturally OFF. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_Elo (600..3000+ default=2100)

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. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_AnalyseMode (OFF=false)

This option is used by the chess GUI to tell the chess engine it is analysing (as opposed to Playing). This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_SearchMoves (ON=true)

This option tells the chess GUI that HIARCS can support search just the moves specified by the chess GUI. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_ShowCurrLine (ON=true)

This option tells the chess GUI that HIARCS can support showing the current line it is analysing. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

UCI_PauseEngine (ON=true)

This option tells the chess GUI that HIARCS can support pausing the engines analysis. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

MultiPV (1..127 default=1)

This option tells the chess GUI that HIARCS can support analysing multiple PV lines at the same time. This setting like all UCI_ settings is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

Ponder (OFF=false)

This option tells the chess GUI that HIARCS can ponder. Pondering is off by default but the chess GUI can enable it. This setting is handled in a special way by chess GUIs like HIARCS Chess Explorer Pro.

AutoSave PGN (OFF=false)

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.

UCI_EngineAbout

This gives some brief information about the HIARCS chess engine including the average max strength it expects to play at on your computer.

Important HIARCS folders

PC and Mac versions

In your Documents folder you will find a HIARCS Chess folder with Books, Engines and EngineData folders. Please put new books in the Books folder. This only applies to HIARCS Chess Explorer and HIARCS Chess Explorer Pro. The default location for all the files is: /Users/username/Documents/HIARCS Chess