From: pb00067 <pb00067@PHXL0356.wp.lan>
Date: Mon, 14 Dec 2020 15:30:56 +0000 (+0100)
Subject: Simplify condition for assigning static-eval based bonus
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=1f3b5b8b54fbf9d3b74bcba831466eeb1104b421;hp=--cc

Simplify condition for assigning static-eval based bonus

for quiet move ordering and simplify bonus formula.

Due to clamping the bonus to relative low values the impact on high
depths is minimal, thus the restriction to low depths seems not
necessary.
Also the condition of movecount in previous node seems to be not
determinant.

Passed STC:
LLR: 2.95 (-2.94,2.94) {-1.25,0.25}
Total: 14600 W: 1424 L: 1323 D: 11853
Ptnml(0-2): 55, 1033, 5020, 1140, 52
https://tests.stockfishchess.org/tests/view/5fd67b381ac16912018885ec

Passed LTC:
LLR: 2.95 (-2.94,2.94) {-0.75,0.25}
Total: 85008 W: 3218 L: 3206 D: 78584
Ptnml(0-2): 49, 2840, 36700, 2880, 35
https://tests.stockfishchess.org/tests/view/5fd6af041ac16912018885f8

closes https://github.com/official-stockfish/Stockfish/pull/3265

bench: 4524994
---

1f3b5b8b54fbf9d3b74bcba831466eeb1104b421
diff --git a/src/search.cpp b/src/search.cpp
index cdbccb4c..e272c10b 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -815,9 +815,10 @@ namespace {
         tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
     }
 
-    if ((ss-1)->moveCount > 1 && is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture && depth < 7)
+    // Use static evaluation difference to improve quiet move ordering
+    if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
     {
-        int bonus = std::clamp(- (depth+1) * 2 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
+        int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
         thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
     }