Adjust reduction less at medium depths

kurt22i · vondele · commit d09653df0d1b · 2022-10-30T16:19:09.000+01:00
This patch dampens the reduction increase/decrease from statScore at mid-range depths. Inspired by patterns noticed in this tune: https://tests.stockfishchess.org/tests/view/635188930e5f47a8d0ffe8f5 Passed STC: https://tests.stockfishchess.org/tests/view/63599dfd6b27ef94d9ec04af LLR: 2.95 (-2.94,2.94) <0.00,2.00> Total: 87464 W: 23519 L: 23134 D: 40811 Ptnml(0-2): 319, 9599, 23524, 9958, 332 Passed LTC: https://tests.stockfishchess.org/tests/view/635a73046b27ef94d9ec2313 LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 154792 W: 41746 L: 41214 D: 71832 Ptnml(0-2): 79, 15181, 46349, 15703, 84 closes #4213 Bench 4271738
diff --git a/AUTHORS b/AUTHORS
@@ -91,7 +91,7 @@ Hongzhi Cheng
 Ivan Ivec (IIvec)
 Jacques B. (Timshel)
 Jan Ondruš (hxim)
-Jared Kish (Kurtbusch)
+Jared Kish (Kurtbusch, kurt22i)
 Jarrod Torriero (DU-jdto)
 Jean Gauthier (OuaisBla)
 Jean-Francois Romang (jromang)
diff --git a/src/search.cpp b/src/search.cpp
@@ -1177,7 +1177,7 @@ namespace {
                          - 4433;
 
           // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-          r -= ss->statScore / 13628;
+          r -= ss->statScore / (13628 + 4000 * (depth > 7 && depth < 19));
 
           // In general we want to cap the LMR depth search at newDepth, but when
           // reduction is negative, we allow this move a limited search extension
