After the creation of the interesting 3 man table bases I move on to the 4 man stuff. The principle is the same but unfortunately they grow very heavily in size compared to the 3 man tables. At the 1st look they are 64 times bigger because a additional piece with 64 possible squares is included. This means uncompressed takes such a table 30 MB, which is quite a lot if you consider the fact that there are a lot of possible 4 man games and all of them require that space.
So I have to deal with board symmetry properties to contain the space required by the tables. I start with the games without pawns. Here the symmetries are the biggest and I need those tables for the games with the pawns anyway.
I'm starting to think of a conversion method that involves core squares like A1, B1, C1, D1, B2, C2, D2, C3, D3 and D4. Only positions with the white king on a core square are processed. If the white king is not on a core square the board is rotated or flipped and rotated until the white king is on a core square. This should save about 80% of space.
When the conversion is working I will explain it in more detail in a later post.