Less NMP if the position was previously in PV.

31m059 · snicolet · commit ee5d047270f5 · 2020-01-29T23:24:38.000+01:00
The intention of the patch is to avoid aggressive null move pruning (NMP) in positions that have previously been found to be important (PV nodes). If we already do not apply NMP for current PV nodes, it makes sense to apply it less often for positions that have previously been PV nodes too. STC: LLR: 2.96 (-2.94,2.94) {-1.00,3.00} Total: 14959 W: 2921 L: 2782 D: 9256 Ptnml(0-2): 254, 1679, 3493, 1762, 282 http://tests.stockfishchess.org/tests/view/5e2f6637ab2d69d58394fcfd LTC: LLR: 2.95 (-2.94,2.94) {0.00,2.00} Total: 6442 W: 899 L: 753 D: 4790 Ptnml(0-2): 42, 549, 1885, 659, 61 http://tests.stockfishchess.org/tests/view/5e2f767bab2d69d58394fd04 closes official-stockfish/Stockfish#2525 Bench: 4725546
diff --git a/src/search.cpp b/src/search.cpp
@@ -843,7 +843,7 @@ namespace {
         && (ss-1)->statScore < 23397
         &&  eval >= beta
         &&  eval >= ss->staticEval
-        &&  ss->staticEval >= beta - 32 * depth + 292 - improving * 30
+        &&  ss->staticEval >= beta - 32 * depth - 30 * improving + 120 * ttPv + 292
         && !excludedMove
         &&  pos.non_pawn_material(us)
         && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
