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Rybka engine
Computer chess
Rybka team

Rybka 3 Engine Parameters

General Parameters

Contempt Play: The degree to which Rybka considers herself the stronger player and therefore prefers complex, unbalanced positions to simplified ones during game play. Positive values indicate a high level of contempt for the opponent and a desire for complex positions. Negative values indicate a high level of respect for the opponent and a desire for simple, balanced and drawish positions. This parameter controls only Rybka's evaluation function and not her search - Rybka will report better scores for herself when contempt is positive. The default value of 15 gives Rybka an ambitious, dynamic playing style, prefering imbalance for the sake of imbalance.

Contempt Analyze: Similar to Contempt Play - the degree to which Rybka considers white the stronger player during analysis. The default value of 0 gives Rybka a completely objective approach to analysis.

Preserve Analysis: When selected, Rybka remember her analysis for a longer period of time. When unselected, older analysis is more quickly discarded in favor of newer results. Preserve analysis is generally preferable for heavy interactive analysis revolving around a single point in a game or variation, where the user is constantly moving up and down in the same area of the tree of variations. For analysis which moves quickly from one position to the next, preserve analysis is usually best unselected. When preserve analysis is selected, it is usually a good idea to clear the hash table when moving on from one set of related positions to another set.

UCI_LimitStrength, UCI_Elo: These parameters work together. When (and only when) UCI_LimitStrength is selected, Rybka plays at the level specified in UCI_Elo. These levels are now fairly realistic from a strength point of view.

Max CPUs: By default, Rybka will start one process for each physical core on the machine. The [Max CPUs] parameter puts an upper limit on the number of processes which are started. It should be used when other applications need large amounts of CPU time. In the single-processor version of Rybka, this value is always set to 1.

MultiPV_cp: When Rybka runs in multi-variation mode, variations which are this number of centipawns worse than the best move are not given exact scores. This saves the engine from wasting CPU time assigning exact scores to clearly inferior moves.

Time Buffer: During game play, Rybka strives to keep this amount of time (specified in seconds) in reserve. It should be set when the system is a bit overloaded, when suffering from lag while playing on a server, or simply to speed up Rybka's play.

NalimovPath: The set of paths to directories which contain tablebase files. This parameter is typically set automatically by the GUI.

NalimovCache: The size in megabytes of a buffer used to store relevant tablebase positions. This parameter is typically set automatically by the GUI.

NalimovUsage: Controls the frequency with which Rybka probes tablebases in her search, from "frequently" (most often) to "normally" (less often) to "rarely" (least often) to "never".

UCI_Query: Not for users. Interfaces can invoke this button to learn about Rybka's UCI-extended capability.

Persistent Hash Parameters

The following set of parameters all deal with storing, loading and merging analysis. More details can be found in the persistent hash section.

Saved Hash File

Save Hash

Load Hash

Persistent Hash Enabled

Persistent Hash File

Persistent Hash Play Depth

Persistent Hash Write Depth

Persistent Hash Size

Persistent Hash Reset

Persistent Hash Resize

Persistent Hash Merge File

Persistent Hash Do Merge