Refine futility pruning for parent nodes

Vizvezdenec · vondele · commit af050e5eed43 · 2021-11-28T14:25:06.000+01:00
This patch is a result of refining of tuning vondele did after new net passed and some hand-made values adjustements - excluding changes in other pruning heuristics and rounding value of history divisor to the nearest power of 2. With this patch futility pruning becomes more aggressive and history influence on it is doubled again. passed STC https://tests.stockfishchess.org/tests/view/61a2c4c1a26505c2278c150d LLR: 2.94 (-2.94,2.94) <0.00,2.50> Total: 33848 W: 8841 L: 8574 D: 16433 Ptnml(0-2): 100, 3745, 8988, 3970, 121 passed LTC https://tests.stockfishchess.org/tests/view/61a327ffa26505c2278c26d9 LLR: 2.94 (-2.94,2.94) <0.50,3.00> Total: 22272 W: 5856 L: 5614 D: 10802 Ptnml(0-2): 12, 2230, 6412, 2468, 14 closes #3814 bench 6302543
diff --git a/src/search.cpp b/src/search.cpp
@@ -1068,7 +1068,7 @@ namespace {
               // Futility pruning: parent node (~5 Elo)
               if (   !ss->inCheck
                   && lmrDepth < 8
-                  && ss->staticEval + 172 + 145 * lmrDepth + history / 128 <= alpha)
+                  && ss->staticEval + 142 + 139 * lmrDepth + history / 64 <= alpha)
                   continue;
 
               // Prune moves with negative SEE (~20 Elo)
