Rein Halbersma wrote:
Alright, so 8 piece DTM checkers databases could have been generated 20 years ago. They weren't.....
Are there any additional insights that are relevant for other db builders?
There are only two researchers on planet earth who ever successfully completed DTW databases for the game of checkers: Gil Dodgen and Ed Trice.
My friend and colleague died in 2016. I promised him "one day" I would solve the 8-piece set after we both did the 4x3 part of the 7-piece database.
I've done Distance To Win endgames for chess (The Sniper, 1987), Gothic Chess (my 80-square variant with Archbishop and Chancellor pieces, 2004), and checkers (2001, 2017). In my opinion, the checkers algorithm is the one requiring the most brain power. It's hard to prevent an "infinite loop" in checkers DTW for reasons I will not elaborate here. Suffice it to say the iteration on which a win or loss is first realized RARELY matches the final Distance To Win number.
Furthermore, since the 8-piece exceeds the DTW distance for a single byte, unless you use operator-overloading for making functional 9-bit or 10-bit bytes, then you need two bytes per position in RAM. When you include the promotion slices and jump sub-databases, even loading and unloading them to minimize the RAM, you still need a 128 GB system, unless you want to grind your hard drive into pulp and magnify the time taken to solve it by a few thousand.
So, yeah, 20 years ago? Yeah right.
And, in the paper I published in 2003, I corrected Published Play going back to 1756. A common endgame called "4th Position" had been played sub-optimally since before the United States was even a country. And guess who corrected the well-known endgame? Me.
No checkers world champions, nor the legendary Marion Tinsley, could conceive of the sharp solution offered by the Perfect Play databases. The closest equivalent in chess I could think of is the Lucena Position.
So now, with the 8-piece, I can rewrite most of the book Boland's Bridges if I want to. By the way, do you have any published play corrections of your own? Or is it just me?