Checkers

During the past two weeks, two new checkers programs were released for the iPhone - both of them based on my simple checkers engine, so I can heartily recommend both :-)
Geoff Rainville's program is called Teeny checkers. You can buy it at the iTunes store!
Jon Schlegel has written Draughts Free and Draughts Premium. The free version will display ads, the premium version won't bother you.

I finally put the endgame database source code online - all of it, that is: The database access code necessary if you want to use the compressed databases in your checkers engine, the database generator program, and the database compression program. They are all available on the download page.

I have not been working much on CheckerBoard recently. With checkers solved, and disturbing things such as peak oil, climate change and the Malthusian catastrophe waiting just around the corner, I doubt that I will ever work on it again (except for bug fixes). Therefore, I am publishing the source code of CheckerBoard, in case anybody wants to continue improving it. You can get it on the download page!

Birthday update: CheckerBoard 1.651 fixes some bugs that were present in the April 27 release of CB 1.65. There is also a 64-bit version of the entire package available. Get it on the download page!

I have released a new version of Cake's Huge Opening Book. This book is based on over 2.8 million analysed positions and is one ply deeper in main lines than the previous version. It now contains exactly 1'869'199 moves, or roughly 20% more than the previous book. Read more and download it on the book page!

Yesterday, the Chinook team announced that they have solved checkers - it's a draw. The result comes as no surprise: The huge opening books of the top programs are already very close to being a proof that checkers is a draw - however, they are only very close, and no mathematical proof. You can review the proof, and read much more about it on the Chinook website, which has been revamped a bit to celebrate the occasion. Checkers is the most complex game to have been solved to date, about a million times more complex than connect 4 which was solved in 1988.
Further reading:

• A paper on solving checkers by the Chinook team from 2005
• Salon.com on the solution of checkers

Unfortunately, I don't find enough time for programming these days. I still have what I believe to be interesting ideas though - so I thought I would write some of these down in the hope that some talented CS student might have a crack at it. Interested? Then check out the three programming projects!

In what is surely a milestone for PC checkers programs, Ed Gilbert is offering the 10-piece endgame database for sale on an external harddisk. Thanks to improvements to the endgame database driver (which Ed credits to Neil Burch), it will work with surprisingly little RAM. You can find all the details here. Also new on Ed's website: new versions of the English and Italian KingsRow (1.16c).

Over the past months, Suicidal Cake played 3 matches on Kurnik. It won the first match in March 2006 against the Canadian program Roshi47 4-0, then it lost the second match in April 2006 against the Balarussian program SuicideKallisto 0-4. Igor Korshunov, the author of SuicideKallisto was kind enough to offer me a rematch, which took place in June 2006, and which was the first reasonably close match in the series, with Suicidal Cake winning one and losing two for a 1.5-2.5 final result. You can read more and replay all the games by following the links to the individual matches.