🔍 Add Reverse Futility Pruning (RFP)

[eduherminio]

Summary:

0bf9142: MaxDepth 6, Scaling factor 75

8+0.08 👍🏽 56.1 +/- 18.8 vs main (1414)

Score of Lynx 1431 - rfp 6 75 vs Lynx 1414 - main: 430 - 275 - 264  [0.580] 969
...      Lynx 1431 - rfp 6 75 playing White: 251 - 105 - 128  [0.651] 484
...      Lynx 1431 - rfp 6 75 playing Black: 179 - 170 - 136  [0.509] 485
...      White vs Black: 421 - 284 - 264  [0.571] 969
Elo difference: 56.1 +/- 18.8, LOS: 100.0 %, DrawRatio: 27.2 %
SPRT: llr 2.96 (100.5%), lbound -2.94, ubound 2.94 - H1 was accepted

---

Overview (8+0.08, 8moves_v3):

Rank Name                          Elo     +/-   Games    Wins  Losses   Draws   Points   Score    Draw   White   Black
   0 Lynx 1421 rfp fixed 75 8        4      12    2398     940     913     545   1212.5   50.6%   22.7%   52.5%   48.6%
   1 Lynx 1422 rfp fixed 100 8      10      12    2400     979     911     510   1234.0   51.4%   21.3%   54.4%   48.4%
   2 Lynx 1417 rfp fixed 100 6       6      12    2400     969     926     505   1221.5   50.9%   21.0%   50.6%   51.2%
   3 Lynx 1419 rfp fixed 100 4      10      12    2400     979     911     510   1234.0   51.4%   21.3%   52.7%   50.2%
   4 Lynx 1416 rfp fixed 150 4      19      12    2400     987     858     555   1264.5   52.7%   23.1%   53.5%   51.8%
   5 Lynx 1418 rfp fixed 200 4      -3      12    2402     935     956     511   1190.5   49.6%   21.3%   51.3%   47.8%
   6 MinimalChess 0.5.0             77      10    3602    1862    1073     667   2195.5   61.0%   18.5%   63.2%   58.7%
   7 Cadabra 2.0.0                  30      10    3599    1591    1282     726   1954.0   54.3%   20.2%   56.3%   52.3%
   8 Lynx 1414 - main              -51      10    3599    1008    1534    1057   1536.5   42.7%   29.4%   43.8%   41.6%
   9 BBC 1.1                       -87      10    3600    1014    1900     686   1357.0   37.7%   19.1%   38.1%   37.3%

dc77eca: MaxDepth 4, Scaling factor 150

8+0.08 👍🏽 41.0 +/- 15.9 vs main (1414)

Score of Lynx 1416 rfp fixed 150 4 vs Lynx 1414 - main: 575 - 416 - 362  [0.559] 1353
...      Lynx 1416 rfp fixed 150 4 playing White: 356 - 150 - 170  [0.652] 676
...      Lynx 1416 rfp fixed 150 4 playing Black: 219 - 266 - 192  [0.465] 677
...      White vs Black: 622 - 369 - 362  [0.593] 1353
Elo difference: 41.0 +/- 15.9, LOS: 100.0 %, DrawRatio: 26.8 %
SPRT: llr 2.95 (100.2%), lbound -2.94, ubound 2.94 - H1 was accepted

37a6f10: MaxDepth 8, Scaling factor 100
8+0.08 👍🏽 41.5 +/- 16.0 vs main (1414)

Score of Lynx 1438 - rfp 8 100 vs Lynx 1414 - main: 583 - 422 - 348  [0.559] 1353
...      Lynx 1438 - rfp 8 100 playing White: 321 - 182 - 174  [0.603] 677
...      Lynx 1438 - rfp 8 100 playing Black: 262 - 240 - 174  [0.516] 676
...      White vs Black: 561 - 444 - 348  [0.543] 1353
Elo difference: 41.5 +/- 16.0, LOS: 100.0 %, DrawRatio: 25.7 %
SPRT: llr 2.95 (100.1%), lbound -2.94, ubound 2.94 - H1 was accepted

6a0c6ec: MaxDepth 6, Scaling factor 100

8+0.08 👍🏽 46.1 +/- 16.9 vs main (1414)

Score of Lynx 1417 rfp fixed 100 6 vs Lynx 1414 - main: 489 - 336 - 335  [0.566] 1160
...      Lynx 1417 rfp fixed 100 6 playing White: 289 - 123 - 168  [0.643] 580
...      Lynx 1417 rfp fixed 100 6 playing Black: 200 - 213 - 167  [0.489] 580
...      White vs Black: 502 - 323 - 335  [0.577] 1160
Elo difference: 46.1 +/- 16.9, LOS: 100.0 %, DrawRatio: 28.9 %
SPRT: llr 2.95 (100.2%), lbound -2.94, ubound 2.94 - H1 was accepted

0bf9142: MaxDepth 6, Scaling factor 75

8+0.08 👍🏽 56.1 +/- 18.8 vs main (1414)

Score of Lynx 1431 - rfp 6 75 vs Lynx 1414 - main: 430 - 275 - 264  [0.580] 969
...      Lynx 1431 - rfp 6 75 playing White: 251 - 105 - 128  [0.651] 484
...      Lynx 1431 - rfp 6 75 playing Black: 179 - 170 - 136  [0.509] 485
...      White vs Black: 421 - 284 - 264  [0.571] 969
Elo difference: 56.1 +/- 18.8, LOS: 100.0 %, DrawRatio: 27.2 %
SPRT: llr 2.96 (100.5%), lbound -2.94, ubound 2.94 - H1 was accepted

---

Taking 4 150 as base (1427):

f1b5504: MaxDepth 2, Scaling factor 150
8+0.08 👎🏽vs 4 150 (1427)

Score of Lynx 1429 - rfp 2 150 vs Lynx 1427 - rfp base 4 150: 1235 - 1360 - 934  [0.482] 3529
...      Lynx 1429 - rfp 2 150 playing White: 755 - 531 - 478  [0.563] 1764
...      Lynx 1429 - rfp 2 150 playing Black: 480 - 829 - 456  [0.401] 1765
...      White vs Black: 1584 - 1011 - 934  [0.581] 3529
Elo difference: -12.3 +/- 9.8, LOS: 0.7 %, DrawRatio: 26.5 %
SPRT: llr -2.94 (-100.0%), lbound -2.94, ubound 2.94 - H0 was accepted

bc78727: MaxDepth 6, Scaling factor 100
8+0.08 👍🏽 12.0 +/- 7.9 vs 4 150 (1427)

Score of Lynx 1430 - rfp base 6 100 vs Lynx 1427 - rfp base 4 150: 2087 - 1898 - 1481  [0.517] 5466
...      Lynx 1430 - rfp base 6 100 playing White: 1277 - 731 - 725  [0.600] 2733
...      Lynx 1430 - rfp base 6 100 playing Black: 810 - 1167 - 756  [0.435] 2733
...      White vs Black: 2444 - 1541 - 1481  [0.583] 5466
Elo difference: 12.0 +/- 7.9, LOS: 99.9 %, DrawRatio: 27.1 %
SPRT: llr 2.96 (100.4%), lbound -2.94, ubound 2.94 - H1 was accepted

6ce48d9: MaxDepth 8, Scaling factor 150
8+0.08 vs 4 150 (1427)

Score of Lynx 1428 - rfp 8 150 vs Lynx 1427 - rfp base 4 150: 3037 - 3033 - 2340  [0.500] 8410
...      Lynx 1428 - rfp 8 150 playing White: 1883 - 1164 - 1158  [0.585] 4205
...      Lynx 1428 - rfp 8 150 playing Black: 1154 - 1869 - 1182  [0.415] 4205
...      White vs Black: 3752 - 2318 - 2340  [0.585] 8410
Elo difference: 0.2 +/- 6.3, LOS: 52.0 %, DrawRatio: 27.8 %
SPRT: llr -1.13 (-38.3%), lbound -2.94, ubound 2.94

Taking 6 100 as base (1430):

0bf9142: MaxDepth 6, Scaling factor 75
8+0.08 👍🏽 5.8 +/- 4.6 vs 6 100 (1430)

Score of Lynx 1431 - rfp 6 75 vs Lynx 1430 - rfp base 6 100: 5788 - 5527 - 4275  [0.508] 15590
...      Lynx 1431 - rfp 6 75 playing White: 3601 - 2130 - 2064  [0.594] 7795
...      Lynx 1431 - rfp 6 75 playing Black: 2187 - 3397 - 2211  [0.422] 7795
...      White vs Black: 6998 - 4317 - 4275  [0.586] 15590
Elo difference: 5.8 +/- 4.6, LOS: 99.3 %, DrawRatio: 27.4 %
SPRT: llr 2.95 (100.2%), lbound -2.94, ubound 2.94 - H1 was accepted

03dc994: MaxDepth 8, Scaling factor 100
8+0.08 3.8 +/- 4.4 (abandoned to test vs 6 75), looking like potential small gain vs 6 100 (1430)

Score of Lynx 1432 - rfp 8 100 vs Lynx 1430 - rfp base 6 100: 6567 - 6371 - 4822  [0.506] 17760
...      Lynx 1432 - rfp 8 100 playing White: 4053 - 2395 - 2432  [0.593] 8880
...      Lynx 1432 - rfp 8 100 playing Black: 2514 - 3976 - 2390  [0.418] 8880
...      White vs Black: 8029 - 4909 - 4822  [0.588] 17760
Elo difference: 3.8 +/- 4.4, LOS: 95.8 %, DrawRatio: 27.2 %
SPRT: llr 1.35 (45.8%), lbound -2.94, ubound 2.94

Taking 6 75 as base (1431/1440):

0c7bf16: MaxDepth 8, Scaling factor 75
8+0.08 👎🏽 -5.5 +/- 7.2, looking like potential small gain vs 6 100 (1431)

Score of Lynx 1439 - rfp 8 75 vs Lynx 1431 - rfp base 6 75: 2288 - 2390 - 1771  [0.492] 6449
...      Lynx 1439 - rfp 8 75 playing White: 1380 - 945 - 899  [0.567] 3224
...      Lynx 1439 - rfp 8 75 playing Black: 908 - 1445 - 872  [0.417] 3225
...      White vs Black: 2825 - 1853 - 1771  [0.575] 6449
Elo difference: -5.5 +/- 7.2, LOS: 6.8 %, DrawRatio: 27.5 %
SPRT: llr -2.94 (-100.0%), lbound -2.94, ubound 2.94 - H0 was accepted

6ea5bb9: MaxDepth 8, Scaling factor 100
8+0.08 👎🏽 -1.8 +/- 5.3 vs 6 75 (1431)

Score of Lynx 1438 - rfp 8 100 vs Lynx 1431 - rfp 6 75: 4391 - 4453 - 3328  [0.497] 12172
...      Lynx 1438 - rfp 8 100 playing White: 2712 - 1710 - 1665  [0.582] 6087
...      Lynx 1438 - rfp 8 100 playing Black: 1679 - 2743 - 1663  [0.413] 6085
...      White vs Black: 5455 - 3389 - 3328  [0.585] 12172
Elo difference: -1.8 +/- 5.3, LOS: 25.5 %, DrawRatio: 27.3 %
SPRT: llr -2.96 (-100.6%), lbound -2.94, ubound 2.94 - H0 was accepted

436e350: RFP before NMP (1442):
8+0.08 👎🏽 -4.8 +/- 6.9 vs 6 75 (1440)

Score of Lynx 1442 - rfp before nmp vs Lynx 1440 - rfp base 6 75: 2460 - 2557 - 1970  [0.493] 6987
...      Lynx 1442 - rfp before nmp playing White: 1516 - 961 - 1017  [0.579] 3494
...      Lynx 1442 - rfp before nmp playing Black: 944 - 1596 - 953  [0.407] 3493
...      White vs Black: 3112 - 1905 - 1970  [0.586] 6987
Elo difference: -4.8 +/- 6.9, LOS: 8.5 %, DrawRatio: 28.2 %
SPRT: llr -2.95 (-100.3%), lbound -2.94, ubound 2.94 - H0 was accepted

1616e1c: Avoid RFP re-evaluation in case of NMP evaluating back

8+0.08 👎🏽 vs 6 75 (1440)

Score of Lynx 1443 - rfp before nmp vs Lynx 1440 - rfp base 6 75: 3239 - 3324 - 2440  [0.495] 9003
...      Lynx 1443 - rfp before nmp playing White: 2047 - 1254 - 1201  [0.588] 4502
...      Lynx 1443 - rfp before nmp playing Black: 1192 - 2070 - 1239  [0.402] 4501
...      White vs Black: 4117 - 2446 - 2440  [0.593] 9003
Elo difference: -3.3 +/- 6.1, LOS: 14.7 %, DrawRatio: 27.1 %
SPRT: llr -2.96 (-100.4%), lbound -2.94, ubound 2.94 - H0 was accepted

609dce9: beta condition
8+0.08 👎🏽

Score of Lynx 1441 - rfp beta vs Lynx 1440 - rfp base 6 75: 2455 - 2556 - 1838  [0.493] 6849
...      Lynx 1441 - rfp beta playing White: 1537 - 954 - 934  [0.585] 3425
...      Lynx 1441 - rfp beta playing Black: 918 - 1602 - 904  [0.400] 3424
...      White vs Black: 3139 - 1872 - 1838  [0.592] 6849
Elo difference: -5.1 +/- 7.0, LOS: 7.7 %, DrawRatio: 26.8 %
SPRT: llr -2.96 (-100.4%), lbound -2.94, ubound 2.94 - H0 was accepted

Wrong impl, inside of move loop

pre-psqt:

011dd9c: MaxDepth 4, Scaling factor 150

8+0.08 👎🏽 vs v0.16.0 (no psqt)

Score of Lynx 1378 - rfp vs Lynx 0.16.0: 4484 - 4545 - 3318  [0.498] 12347
...      Lynx 1378 - rfp playing White: 2725 - 1727 - 1722  [0.581] 6174
...      Lynx 1378 - rfp playing Black: 1759 - 2818 - 1596  [0.414] 6173
...      White vs Black: 5543 - 3486 - 3318  [0.583] 12347
Elo difference: -1.7 +/- 5.2, LOS: 26.0 %, DrawRatio: 26.9 %
SPRT: llr -2.95 (-100.2%), lbound -2.94, ubound 2.94 - H0 was accepted

---

post-psqt:

0a832b8: MaxDepth 2, Scaling factor 300

8+0.08 👎🏽 vs main (1399)

Score of Lynx 1402 rfp 300 2 vs Lynx 1399 - main: 3052 - 3139 - 2377  [0.495] 8568
...      Lynx 1402 rfp 300 2 playing White: 1894 - 1226 - 1164  [0.578] 4284
...      Lynx 1402 rfp 300 2 playing Black: 1158 - 1913 - 1213  [0.412] 4284
...      White vs Black: 3807 - 2384 - 2377  [0.583] 8568
Elo difference: -3.5 +/- 6.2, LOS: 13.4 %, DrawRatio: 27.7 %
SPRT: llr -2.96 (-100.6%), lbound -2.94, ubound 2.94 - H0 was accepted

b361e36: MaxDepth 4, Scaling factor 150

8+0.08 👎🏽 vs main (1399)

Score of Lynx 1403 - rfp 4 150 vs Lynx 1399 - main: 1630 - 1744 - 1309  [0.488] 4683
...      Lynx 1403 - rfp 4 150 playing White: 989 - 678 - 674  [0.566] 2341
...      Lynx 1403 - rfp 4 150 playing Black: 641 - 1066 - 635  [0.409] 2342
...      White vs Black: 2055 - 1319 - 1309  [0.579] 4683
Elo difference: -8.5 +/- 8.4, LOS: 2.5 %, DrawRatio: 28.0 %
SPRT: llr -2.95 (-100.2%), lbound -2.94, ubound 2.94 - H0 was accepted

382c41e: MaxDepth 6, Scaling factor 100

8+0.08 👎🏽 (aborted) vs main (1399)

Score of Lynx 1404 - rfp 6 100 vs Lynx 1399 - main: 2119 - 2171 - 1390  [0.495] 5680
...      Lynx 1404 - rfp 6 100 playing White: 1293 - 874 - 673  [0.574] 2840
...      Lynx 1404 - rfp 6 100 playing Black: 826 - 1297 - 717  [0.417] 2840
...      White vs Black: 2590 - 1700 - 1390  [0.578] 5680
Elo difference: -3.2 +/- 7.8, LOS: 21.4 %, DrawRatio: 24.5 %
SPRT: llr -1.77 (-60.1%), lbound -2.94, ubound 2.94

: MaxDepth 8, Scaling factor 75

8+0.08 👎🏽 vs main (1399)

Score of Lynx 1402 rfp 300 2 vs Lynx 1399 - main: 3017 - 3104 - 2358  [0.495] 8479
...      Lynx 1402 rfp 300 2 playing White: 1863 - 1176 - 1200  [0.581] 4239
...      Lynx 1402 rfp 300 2 playing Black: 1154 - 1928 - 1158  [0.409] 4240
...      White vs Black: 3791 - 2330 - 2358  [0.586] 8479
Elo difference: -3.6 +/- 6.3, LOS: 13.3 %, DrawRatio: 27.8 %
SPRT: llr -2.95 (-100.2%), lbound -2.94, ubound 2.94 - H0 was accepted