Zahak 4.0, and ZaTour Season 2

Jun 30, 2021 · 3 min read  ·
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In the past few weeks I have been actively working on Zahak, and I have made a very good progress. I think it warrants a version cut at this point, this version comes with a bunch of new features and fixes, and in self play shows a progress of around 235 Elo points, which I think it is a bit generous, and the progress should be around 200 at most.

Here is the changelog since 3.0:

  • King Safety, and Pawn Shield
  • Pawn structure evaluation is redone, with various mis-evaluation fixes
  • More aggressive Null Move Pruning
  • NPS increase and performance optimizations (almost 40% more NPS)
  • Add Internal Iterative Deepening
  • Add Enhanced Futility Pruning
  • Pseudo Legal Moves
  • Fix SEE pruning
  • Fix Hash-move and move ordering for pawn promotion
  • Search Parameter tweaking

It is also worth mentioning that Zahak 3.0 is currently competing in Graham’s D8 tournament, and so far he is somewhere in the middle of the league. Hopefully he can manage to stay in the league.

To download Zahak 4.0, please visit here

ZaTour Season 2

Zahak 4.0 will be participating in ZaTour Season 2, which comes in a new format. There will be two leagues:

The Promotion League

Consists of five engines:

  • Minimal Chess 0.4.9
  • Rustic Alpha 3.1.112
  • KingSlayer
  • FairyMax
  • Zahak 1.0.1 (guest participant)

The time control is 25m+10s, and the engines will play 30 games against each other, alternating the colors. The first engine will qualify to the next league (Super League). Except for Zahak 1.0.1, which cannot qualify even if he finishes the first, as Zahak 4.0 is already competing in Super League. Zahak 1.0.1 is only added to the league to increase the number of games and participating engines in the league.

Unfortunately due to a mistake on my part, Minimal Chess played the first few games with an outdated binary, and to compensate for that, we decided to compensate it by, allowing it to qualify to the Super League, alongside the winner of the league, in the event if it ended the league with 2 or less points behind the winner. I believe this is a fair compensation, as the other engines will keep their scores, while Minimal Chess won’t get penalized for a mistake that was done by me. The only price to pay, is we might end up with an extra engine in the Super League.

Super League

Consists of five or six engines:

  • Nalwald Skylake 1.9
  • Barbarossa 0.6.0
  • Loki 3.5
  • Lozza 3
  • Zahak 4.0
  • The winner of Promotion League
  • Possibly another engine from Promotion League

The time control will be the same as in the Promotion League, and again each two engines will play 30 games against each other, with alternating colors. The engine that finishes the last in the Super League will be relegated to the Promotion League, and the two engines that will finish at the top will meet each other in a 100 game long match in ZuFi (ZaTour Super Final), which will be using the same time control as the Super League.