Kingsrow is a checkers engine written by Ed Gilbert. There are versions for 8x8 English, Italian checkers, and for 10x10 international draughts. The 8x8 versions work with CheckerBoard as the user interface. All are free downloads.



12/19/2020: Jonathan Kreuzer has built a neural network evaluation for his Checkers program, now called GuiNN Checkers. It is much stronger than before, now similar in strength to Cake. To make it more useful for engine match testing, I have added the kingsrow egdb driver to it, so that it can use the kingsrow 10-piece WLD db. Install programs and source code.

8/23/2020: New versions for English and Italian kingsrow are available for download. There are some bug fixes and a modest improvement in search strength. The Italian version also has a new opening book built with a recent stronger kingsrow engine, and more book positions.

9/13/2019: I have completed an analysis of 11-man ballots. It includes an opening book file for kingsrow, classification of each ballot as drawn or won/lost, and difficulty ratings. Bob Newell's Checker Maven webzine has an article about it: Checker Maven.

5/14/2019: Depth-to-win databases for English and Italian checkers have been built and are available for download, along with updated versions of Kingsrow and CheckerBoard that support the new databases, and 400K positions were added to the English opening book.

11/20/2018: Kingsrow for English and Italian checkers have been redesigned using Machine Learning techniques, and are quite a bit stronger as a result. Bob Newell's Checker Maven webzine has an article about it: Machine Learning Comes To Kingsrow.

9/15/2016: I have updated the egdb_library docs and source files (for accessing the endgame databases from a program). Download.

7/18/2016: A 10-piece endgame database for English checkers is now available for download, along with new versions of Kingsrow (1.17) and CheckerBoard.

7/4/2016: A full 10-piece endgame database for Italian checkers is now available for download, along with new versions of Italian Kingsrow (1.17) and CheckerBoard.

5/30/2013: A new version of Kingsrow (1.16h)  for English and Italian checkers is available. The Italian opening book has 25% more positions. Both versions have improvements in playing positions that are database draws.

9/30/2012: A new version of Kingsrow (1.16g)  for English and Italian checkers is available. It plays more aggressively in positions that are a database draw. The Italian version also has a bug fixed in the move generator.

 5/30/2011: A new version of Kingsrow (1.16f)  for English and Italian checkers is available, and also a new version of CheckerBoard (1.72) at Martin's web site. Kingsrow has some errors fixed in the English opening book, allows up to 8 search threads and 1024mb for the hashtable, has improved detection of draws by repetition, and a faster "allscores" search. The Italian version of Kingsrow now has a 64-bit version, and download links for an 8-piece endgame database. The new version of CheckerBoard fixes several bugs and allows access to the 8 search threads and larger hashtable settings.

7/6/2009:  I have finished building a full 8-piece database for 10x10 international draughts. Details here.

 7/1/2009:  A new version of Kingsrow for English and Italian checkers is now available, and also a new version of CheckerBoard. Kingsrow now has a parallel search engine, which can give up to a 3x speedup with multi-core CPUs. Details of the changes are given here, and setup files can be downloaded at the English and Italian checkers links above.

8/30/2008:  I have added an expansion of Wyllie's famed "Invincible" to the 10-piece book. Details and opening book file download here.

12/5/2007: A new version of Kingsrow which plays 10x10 international draughts won a tournament in the Netherlands against 9 European programs. You can read about it here.

7/7/2007: I have updated the install file for Italian Kingsrow. The Kingsrow program is unchanged, but the opening book has been increased to 725,000 positions.

5/22/2007: The 10-piece db for English checkers is now available! See details here. There are also new versions of Kingsrow (1.16c) for both English and Italian checkers with engine and opening book improvements.

12/5/2005: 9-piece and partial 10-piece Italian databases are coming. In October I finished building the 5x4 subset of the 9-piece Italian database. I also built some of the most useful parts of the 10-piece Italian db -- 5x5 positions with one king or less on a side. Normally this requires computing all the positions with more kings also, a process that took me nearly a full year using 4 computers for English checkers. But I computed these 10-piece positions in about 3 weeks by skipping the more king-heavy positions. There is a disadvantage to doing it this way -- some of these positions rely on the missing positions with more kings, and therefore cannot be resolved. However it turns out that only a small percentage of the positions cannot be resolved, so this was a nice way to make the Italian KingsRow more powerful with only a small additional computing effort. Here is a table which shows the percentage of positions that are resolved in each 10-piece slice.

I have been building a new opening book using these databases. When I first built an opening book for Italian checkers using an 8-piece db, I discovered that 9 of the opening ballots are probably forced losses for the weak side. Using the new larger databases I have found 2 more ballots that are probably lost. These are 21-18 12-15 22-19 and 23-20 12-15 22-19. The new opening book and endgame databases will be available in early 2006.

7/17/2005: The 10-piece database is finished. Read the story of how it was built.

1/12/2005:  10-piece database progress. In August I started computing the 10-piece endgame database. It is being built by a cluster of 4 PCs. At the current rate of progress it will be completed this summer, and it will occupy 150GB of disk space. About 42% of the database has been built, and most of this data has been verified against Jonathan Schaeffer's database. I am also saving the 'moves-to-conversion' data, which is generated with almost no additional effort as a byproduct of computing the win-loss-draw data. The MTC data is useful for solving very difficult positions that require a large number of moves before a conversion move occurs. More information about the MTC data along with some of these most difficult 10-piece endings and the moves to play them correctly is here.

11/28/2004:  Cake wins the long CheckerBoard engine match! Cake won a 624-game computer checkers match against Kingsrow by a score of +3 -1 = 620.  The match games can be downloaded here. Details of the match announcement are here.

2/12/2004:  Attention checkers programmers: I am making available the endgame database drivers that are used in Kingsrow. These drivers, which are provided in the form of a .dll file, provide access to the Cake, Chinook, and Kingsrow English and Italian databases. Download here. (Note: these drivers are only useful to people that are writing checkers programs. If you are only using a checkers program you don't need this package.)


Ed Gilbert
Last revised: December 19, 2020.