I expected this approach to improve move ordering, and thus allow my engine to search a bit deeper. What I found was that it didn't change the depth (in fact the countermove history version is searching very slightly shallower). But despite going shallower, I'm seeing a slight ELO increase.
I'm thinking that with all the reductions we have in engines these days (LMR, LMP, nullmove etc.) interesting properties emerge when tweaking things like move ordering in the search. My theory on the above is that *maybe* the counter move stuff is improving move ordering, meaning I'm not pruning or reducing better moves as much as before, hence the ELO increase.
Anyway, just a little musing for a Saturday morning What do others think?
Here's my data around depth searched from versions with and without the countermove stuff. _13 has the countermove bits.
Code: Select all
Engine Depth Time Games Moves Average Forfeit Book Depth MIDG EARLY ENDG LATE mar2019_12 19.72 103:55:40 5743 341647 1.10 0 47412 8.26 17.15 | 18.02 | 20.30 | 28.22 mar2019_13 19.52 103:39:11 5743 341512 1.09 0 47345 8.24 16.99 | 17.82 | 20.07 | 27.92