4.7: Endgame Tablebases

A Tablebase is a special type of database which contains perfect information about the result (win to White, win to Black or draw) for every possible legal chess position with a particular set of material. For example, the KQKR contains information for every legal King and Queen versus King and Rook position.

Because the amount of storage goes up exponentially with each extra piece, tablebases are currently limited to 6-men endgames (that is positions with six or fewer pieces or pawns on the board including the kings) and most people only use up to 5-men tablebses since the 6-men files are huge.

Tablebase formats

The most common tablebase format in current use by chess programs is called the Nalimov format, after its creator Eugene Nalimov. Nalimov tablebases are very compact but fast to access. They contain distance-to-mate information for each position. Scid can use all Nalimov tablebases up to five men, such as KRPKR (King, Rook and Pawn versus King and Rook) for example.

Nalimov tablebase format files have the extension ".emd". Actually they will end with the suffix "nbw.emd" for White-to-move tablebases, and "nbb.emd" for Black-to-move tablebases. It pays to have both the White to move and Black to move tablebase for a particular material constellation (e.g. "krpkr.nbw.emd" and "krpkr.nbb.emd") for complete information whichever side is to move.

You may find a Nalimov tablebase file with the suffix ".nbw" or ".nbb" with no ".emd". This is an uncompressed tablebase, which is usually huge compared to its compressed (.emd) equivalent. It is far better to get the compressed tablebases, since they are much smaller and just as fast to access.

Obtaining Tablebases

Nalimov tablebases are available for downloading at the Crafty FTP site, from the location insert URL here. To be completed...

Setting up Tablabases in Scid

Once you have a directory (or 2 or 3) of tablebase files, you need to inform Scid which directories to look in for tablebases when the application starts. To do this, select Tablebase Directory... from the Options menu in the Scid main window. For each tablebase folder you have, select a Nalimov (.emd) file in the folder. It doesn't matter which file you select; all tablebases in that folder will be loaded each time you start Scid.

It may be confusing to select a file instead of a folder, but the reason is so you can be sure you are selecting a folder which actually contains tablebase files.

Scid Tablebase Window

To be completed...

Further Reading

See the Using Tablebases in Scid help page.