Kingsrow for English/American checkers

Kingsrow is a checkers engine which is designed to be used with Martin Fierz's user interface program called CheckerBoard. Both Kingsrow and CheckerBoard are free programs and can be downloaded using the links below. 

CheckerBoard

The CheckerBoard install files below are more current than the ones at Martin's site. They have new bug fixes, enhancements for PDN3.0, and the PDN search function now works with all the different checkers variations supported by the program.

For programmers, the CheckerBoard source code is available at GitHub.

Opening Books

Kingsrow has an opening book database of 2.2M positions. It covers all 174 of the 3-move openings. The book was built by doing systematic searches with Kingsrow. This technique is called dropout expansion and was developed by Thomas Linke. It is described in his paper "Exploring the Computational Limits of Large Exhaustive Search Problems". Martin Fierz has written an overview of how dropout expansion works.

There is also a second opening book for 11-man ballots

WLD Endgame Databases

New as of July 2016, I have re-compressed the 10-piece database, using better compression techniques that result in smaller files. The files are now small enough that they can be downloaded from a file server. Previously the WLD files required 214gb of hard drive space, and I had distributed them on an external USB drive. They are now 102gb. If you have the older format db you can continue to use it. There is some advantage to using the newer db because it makes better use of your cache memory.

Kingsrow can also use the 8-piece WLD databases available from Jonathan Schaeffer (Chinook website) and Martin Fierz (CheckerBoard website). During engine setup you should set the path to the directory where the endgame database files are located. Kingsrow automatically detects the type and size of the database that is present.

You can download install files for the 10-piece endgame databases using the links below. To use the 9 and 10-piece databases, you also need to install the databases of 2 through 8 pieces. The files are hosted at Mega. For downloading these large files, Mega only supports Chrome and Opera web browsers, or use the Mega PC App, which is probably the least effort. More about downloading from Mega.

Each install contains a group of .bin files and an .exe setup program file. Download all the files to your PC, then run the setup program to install the database on your hard drive.

If you have the earlier version of the endgame databases, either delete those files first, or install these files in a different directory. Kingsrow will work with either version of the databases, but the older version files take up a lot of space on your hard drive, and there is no reason to keep them if you have the new databases. After you install the new databases, you should tell kingsrow where you put them. Use the Checkerboard menu Engine, Options, More Options, and use the Browse... button under WLD Database to enter the directory path to the db files. There is more information in the help file (menu Engine, Help).

Auxiliary (DTW, DTC) Endgame Databases

In addition to the WLD databases, Kingsrow has 2 types of auxiliary databases that are used when the game position is a win or a loss. 

  1. The DTW (depth to win) database allows Kingsrow to plays the absolute shortest path to a win (or longest path to a loss). 
  2. The MTC (depth to conversion) database allows Kingsrow to play the shortest path to the next non-reversible move.

The WLD db gives the win/loss/draw status of the position, but it does not have any information about the best moves to finish the game. When kings are present it is possible that the winning side might keep making moves that maintain its winning status without making progress towards finishing the game. Kingsrow has heuristics that guide it towards the end of the game, so usually these auxiliary databases are not absolutely necessary, but in a small percentage of cases the distance to a win or conversion is beyond Kingsrow's search horizon. Even if Kingsrow can find a way to win, these databases allow Kingsrow to play the minimum path to wins directly, or indirectly via conversions.

You can only use one auxiliary db at a time, so pick the one that has the attributes of most interest to you. Neither db requires much memory to use, they mainly consume disk space. The DTW db is nice in that it gives the absolute shortest path to a win. But because the DTW information is needed for every endgame position, and it does not compress well, it can only be provided for 2 through 8 pieces. The conversion db only has to have information for positions where the depth to conversion is 10 or more plies, so it can exclude most endgame positions. This allows it to compress much better. The MTC db has data for 2 through 10 pieces.

The files are hosted at Mega. For downloading these large files, Mega only supports Chrome and Opera web browsers, or use the Mega PC App, which is probably the least effort. More about downloading from Mega.

Each install contains a group of .bin files and an .exe setup program file. Download all the files to your PC, then run the setup program to install the database on your hard drive. After you install the new databases, you should tell kingsrow where you put them. Use the Checkerboard menu Engine, Options, More Options, and use the Browse... button under Auxiliary Database to enter the directory path to the db files.

Below are lists of the longest DTW and MTC positions in each database subdivision. You can copy the FEN positions to the Windows clipboard and paste them directly into CheckerBoard.


Ed Gilbert
Last revised: January 12, 2020.