Review

Pocket sparring partner

Among chess playing apps, the open source Black Diamond is your most versatile choice, but don’t expect any fancy graphics, writes Heinrich Tillack.

Black Diamond is simple but functional.
Black Diamond is simple but functional.

Black Diamond is based on the app Droidfish, that made the open source engine Stockfish available on android a decade ago, but it goes way beyond it. Whereas the latest Droidfish version has four engines, Black Diamond comes with a staggering choice of 27 engines. Six of them are based on Stockfish 12.

This could be expected from the app’s author Michael Byrne, a US-based chartered accountant who is known for Stockfish adaptations like Honey, Bluefish or Weakfish, has been inspired by The Queen’s Gambit to create a Harmon engine, and is also a collaborator of Droidfish . However, the focus of his new app is on handicapping the engines in a smart way, which makes Black Diamond a challenging but not unbeatable sparring partner for the average club or hobby player.

Black Diamond’s focus is handicapping the engines in a smart way, which makes it a challenging but not unbeatable sparring partner for the average club or hobby player.

You can set a rating level. You can set ultrashort thinking times under a second per move. You can also delay the engine’s moves if you like to think about the position after your move before encountering a response. If you play against the Stockfish 12 engines Bluefish, Honey, Weakfish or Harmon at limited strength, Black Diamond adapts to your level by using three different criteria. It isn’t just throwing in random blunders. Its less than optimal moves resemble those of humans. Thanks to Night Nurse, a neural network by Dietrich Kappe who also makes networks for the Komodo engine, it plays aggressively in a human way.

A peek into Black Diamond’s menu.
A peek into Black Diamond’s menu.

I wouldn’t recommend Black Diamond for beginners at chess or computer chess. The app doesn’t have any fancy graphics. It’s simple but functional. You can analyse your games with it, but there are more comfortable choices because Black Diamond isn’t designed as a PGN reader. Which makes it a no-go for analysing correspondence games. But you can add your own opening books and train and analyse your variations.

You don’t find Black Diamond on Google Play. Since it is a clone, Google doesn’t distríbute it. But don’t worry. Everything included is open source and legal. You won’t even be bothered by in-app sales or advertising. And the download from Github is straight forward.

Heinrich Tillack is a German developer specializing in Apple games.
Heinrich Tillack is a German developer specializing in Apple games. (photo: private)