Updated: Jan 20
What are chess engine parameters ?
Is it worth changing them?
When is it worth changing engine parameters ?
What does changing parameters do ?
What influence do they have on the strength and style of the engine?
Before we answer these questions, I propose we watch a chess game between the Zappa and Nimzo engines.
15 white's move. Zappa sacrifices Knight.
Fen: r2q1rk1/p2nbNp1/b1p1pn1p/8/2pP4/2B3PB/P1QNPP1P/R4RK1 b - - 0 15
White's 20th move. Zappa sacrifices a second figure.
Fen: r6r/p2nbk2/b3Bnpp/q1p1B3/2pP4/5NP1/P1Q1PP1P/R4RK1 b - - 0 20
Paul Morpy, Mikhail Tal - giants of the tactical games.
The difficulty of playing against such strong and aggressive chess players is that all it takes is one mistake or sometimes one inaccurate move and the game is lost or - at most - ends in a draw (with a lot of luck).
Nimzo has just committed such an inaccuracy. He had the game won, but instead of playing 21...Nxe5 he chose 21... Bb7, which according to Stockfish engine, equalized the game.
Zappa took advantage of this inaccuracy by playing a strong 22.e4!
In the end, after all the storming on the chessboard, this game ended in a draw.
Zappa played with a parameters called Dessident Aggressor, (parameters author: Robert Flesher) which transformed the playing style of this engine to that of a mad attacking grandmaster who doesn't hesitate to sacrifice pawns and pieces to smash the opponent's King.
Zappa version Mexico II on my hardware (4 processors) with default parameters plays with a strength of about 2950 Elo. Nimzo in version 8 on my hardware plays with a strength of 2500 Elo.
Based specifically on this change in Zappa's engine parameters (Dessident Aggressor), you can see that his style of play has changed dramatically, the strength of play has decreased by about 300 Elo points.
Ultimately, this match consisting of 10 chess games won by Zappa, but Nimzo was not without chances.
I am making 10 games of this match available for download in .PGN format.
From a chess man's point of view, this match played by engines at grandmaster level in fascinating style. It was certainly not a boring duel.
The author of this article found it hard to tear himself away from looking at chess games played in beautiful style, full of sacrifices and various tactics.
Okay. That is, we know that changing the parameters affects the strength and playing style of the chess engine.
Now let's see what parameters we can change in several different engines: both older and newest ones.
Phalanx XXII engine - we do not have the ability to change any parameter.
Booot engine - we can only change the number of Threads (cores).
Tiger engine in Gambit version - we have several parameters to change, including Gambit level.
Goliath Light 1.5 engine, also we can change several parameters, including Selectivity for example.
Modern Nemorino 6.00 engine - and here we can change several parameters, including selecting EvalFile.
Another modern and very powerful Fire 8 engine - also we can change several parameters, including Contempt.
Currently (March 2022) the most powerful chess engine Stockfish 14.1 - gives us the possibility to change parameters including e.g. Skill Level.
Zappa Mexico II, which was one of the participants in the match described above. We can configure Zappa with many parameters, including for example Enable mate Extensions.
Nimzo, an engine that has many different parameters to change, including the value of figures. As you can see in the picture, for example, Nimzo values Bishop (435) a bit more than Knight (420).
Deep Hiarcs 14 WSCS, an engine with a reputation for playing in a very human-like style - has some interesting paraemtras to change, including Position Learning.
Dragon 2.6.1 by Komodo, is a super powerful engine that has many parameters in the configuration menu to change, including Use MCTS.
And the last of the engines I chose for the purpose of this article - TheKing 3.50, which is the engine that drives the Chessmaster series programs. It has a lot of parameters to change including, for example, Selective Search.
The potential for change in TheKing engine, has encouraged many talented chess players to change its parameters. As we can see in the listing below, in the case of Chessmaster 11 the default parameter settings of the TheKing engine turned out to be weaker than the parameters set by users !
From the data I've shown, we can infer that it's worth changing the engine parameters if we want to try to increase the engine's play strength and/or change the engine's play style.