Aart's Blog

Although the Certabo electronic boards are mainly intended for chess, the flexibility of the identifying chips makes them suitable for 8x8 checkers as well (draughts, or American checkers, with slightly different rules from e.g. 10x10 international checkers). Therefore, I am planning to add support for Certabo boards in Checkers for Android as well. The 34 identifying chips can be used for the 24 regular pieces and 10 kings for promotion (using special purpose pieces avoids stacking the regular pieces). A 3D printed set can be used for this purpose (a continued hat-tip to my brother-in-law Gerard Harbers for making all the chess and checkers sets for me!). The general idea is illustrated with this picture. Please let me know if you like this upcoming support!

I can't believe it, but Chess for Android just passed its ten year anniversary! In November 2008, it appears for the first time on the -then-called- Android Market, together with Reversi for Android. Checkers for Android was soon to follow. The Android Market was later renamed Google Play . Working on this GUI has been a lot of fun, even though it took all spare time away from further developing my chess engine BikJump. But pioneering support for third party engines (at a time nobody was compiling for ARM), both UCI and XBoard, accessing endgame tablebases on SD card, adding PGN and setup features,simplifying engine setup through Chessbase compatible format and the Android Open Exchange format, using OCR apps to read chess positions, translating text to other languages, maintaining an online manual , and recently adding support for Certabo, DGT, and Millennium electronic chessboards has been just as rewarding. I have compiled many engines for Android back in the days, ran ful...

New releases for both Checkers and Reversi for Android . Both games made some improvements in the notation display, most obvious the use of parenthesis for the alternating moves (suggested by Rein Halbersma), a better column layout, and improved "scrolling" while navigating. Also, both games now support exporting the game to the clipboard or via sharing with another program. For checkers, the PDN (portable draughts notation) is used, for reversi something similar to PGN (portable game notation). For checkers this also required "disambiguating" captures using an intermediate square (which should cover most normal games).

Folks that know me probably saw this coming, but Checkers for Android now also has a notation window and full game navigation, just like Chess for Android and, recently, Reversi for Android. All three games have the same look-and-feel again! Unlike the algebraic notation in chess or reversi, checkers uses a numbered notation, explained in detail in The Checker Maven  (note that, for simplicity of display, my checkers app always just shows the "from" and "to" square for each move or capture, even though technically intermediate squares are sometimes needed to disambiguate multiple jumps). At first glance the numbering may seem a bit confusing, but the notation becomes easier with practice.

Inspired by Rein Halbersma's kind encouragement, I have started some work on an international checkers engine. After all, " dammen " is the variant I grew up with in The Netherlands. Since I have implemented BikJump for chess, BikMove for American checkers, I decided to name this upcoming engine BikDam . I already had some fun hacking a, hopefully, efficient move generator. The rules for captures were very interesting to implement. Here are the perft number from the start position of 10x10 international checkers (a.k.a. dammen). In contrast with my American checkers move generator, here duplicate captures are removed. perft(1) = 9 in 0 ms. perft(2) = 81 in 0 ms. perft(3) = 658 in 0 ms. perft(4) = 4265 in 0 ms. perft(5) = 27117 in 1 ms. 27117.0 KN/s perft(6) = 167140 in 3 ms. 55713.3 KN/s perft(7) = 1049442 in 22 ms. 47701.9 KN/s perft(8) = 6483961 in 78 ms. 83127.7 KN/s perft(9) = 41022423 in 434 ms. 94521.7 KN/s perft(10) = 258895763 in 2599 ms. 99613.6 KN/s perf...