Chess endgame table base KQKR

When I continued my work on the 4 man endgame table bases I started to work on a rather interesting 4 man combination. It is the King and Queen vs King and Rook end game. It is interesting because it is not trivial. All previous tables were mostly trivial as they contain easy forced wins (King and Queen vs King) or contain mostly draws (King and Queen vs King and Queen).


Consider the following position

Black threatens check mate with ... Rh4#. With white to move white can prevent the mate and win. But the table base shows that it requires at least 35 moves to do so. With regards to the 50 moves rule this requires accurate play and here the table base is quite helpful.

The generation of the table took quite some time on my computer also because I use board symmetries when storing the data but so far not in the calculation of the table. So I consider all 33.554.432 positions (2 * 2^24) and this took several hours.