Since I released Prophet 4.2 I’ve made a couple of additional evaluation changes:
- The passed pawn bonus has been made more granular. Where it used to be a simple bonus for a passed pawn, now it varies depending on the pawn’s rank. 40,000 bullet games says that change was worth about 14 ELO.
- Bishop and queen mobility has been made non-linear. This change was inspired by Erik Madsen’s MadChess blog – https://www.madchess.net/2014/12/16/madchess-2-0-beta-build-29-piece-mobility/ . The idea is to encourage piece development. I had originally plugged Erik’s values in verbatim, but they didn’t mesh well with existing weights and testing showed it weakened the program. After running the auto-tuner, this change brought in an additional 22 ELO.
In my first attempt at running the auto-tuner, I just started with the previously tuned weights, plus Erik’s values for bishop and queen mobility, but the tuner couldn’t seem to find any improvements. The error bounced around a little, going up and down, and not making any progress. I eventually decided to do a complete reset. I set the piece values to the traditional 1/3/3/5/9 values, and everything else to 0. Then I re-tuned and validated with some bullet games. The learning curve:
Fresh off the heals of these improvements, Prophet played in an informal online engine blitz tourney today. Unfortunately it was a pretty rough outing, placing just 16/20 with 2.5 points out of 9. It was a very strong field though. Even the 10th place finisher is nearly 3000 ELO on CCRL’s 40/2 list.
:Tourney Players: Round 9 of 9
:
: Name Rating Score Perfrm Upset Results
: ----------------- ------ ----- ------ ------ -------
: 1 +LczTinker [2971] 6.5 [2937] [ 0] +07w =05w =06b =03b +02w =04b =09w +11w +12b
: 2 +NightmareX [2909] 6.5 [2939] [ 0] +12w =06w +09b =04w -01b =05w +07b +08w +11b
: 3 +ChessSystemTalX [2900] 6.5 [2898] [ 35] +10w +09w =08b =01w =06b +07w =05b =04w +13b
: 4 +RubiChess [2875] 6.5 [2947] [ 77] +13w +11w =05b =02b +08w =01w =06b =03b +09w
: 5 +ArasanX [2859] 6.0 [2836] [ 110] +14w =01b =04w =08b +12w =02b =03w =09b +16w
: 6 +WaspX [2830] 6.0 [2679] [ 181] +15w =02b =01w +17b =03w =08b =04w +13w =10b
: 7 +TheBaron [2569] 5.5 [2457] [ 3] -01b +14w +16w =11b +17w -03b -02w +18b +15b
: 8 +Goldbar [2861] 5.0 [2533] [ 19] +16w +17b =03w =05w -04b =06w =13b -02b +18w
: 9 +Marvin [2752] 5.0 [2683] [ 162] +18w -03b -02w +16b +11w +12b =01b =05w -04b
: 10 +Nalwald [2500] 5.0 [2325] [ 165] -03b +18w =15b -12b -13w +17b +16w +14b =06w
: 11 +atomGoldbar [2575] 4.5 [2480] [ 0] +20w -04b +13w =07w -09b +16b +14w -01b -02w
: 12 +WaDuuttie [2567] 4.5 [2411] [ 0] -02b +15w =14b +10w -05b -09w +18b +17w -01w
: 13 +rpiArminius [2272] 4.0 [2425] [ 522] -04b +20w -11b =14w +10b +15w =08w -06b -03w
: 14 +atomFloyd [2242] 4.0 [2267] [ 177] -05b -07b =12w =13b +15w +18w -11b -10w +17b
: 15 +Skiull [1966] 3.0 [2170] [ 410] -06b -12b =10w +18w -14b -13b +17w =16b -07w
: 16 -Prophet [2253] 2.5 [2325] [ 351] -08b +19w -07b -09w +18b -11w -10b =15w -05b
: 17 -Skipper [1662] 2.0 [2219] [1120] +19b -08w +18b -06w -07b -10w -15b -12b -14w
: 18 +atomSargon [1840] 0.0 [1974] [ 0] -09b -10b -17w -15b -16w -14b -12w -07w -08b
: 19 +atomNightmare [forf] 0.0 [1557] [ 0] -17w -16b
: 20 +POS [forf] 0.0 [2023] [ 0] -11b -13b
:
: Average Rating 2474.2 Next up- I’m going to continue with the mobility theme a little longer by testing rook mobility, then knight outposts, trapped bishops, and connected rooks on open files. I don’t expect any of those will be big points by themselves but cumulatively they might be worth a bit.