Adjust singular LMR for positions seen in PV

Vizvezdenec · vondele · commit ff271093139d · 2020-03-17T19:34:47.000+01:00
This patch continues work on altering search for ttPv nodes, using recent idea to alter it more in not PvNodes. Previous tweak based on this idea adjusted singularBeta - this one adjusts value of singularLMR, so they are both related to singular extension search. passed STC http://tests.stockfishchess.org/tests/view/5e700737e42a5c3b3ca2e659 LLR: 2.95 (-2.94,2.94) {-0.50,1.50} Total: 140608 W: 27053 L: 26659 D: 86896 Ptnml(0-2): 2425, 16337, 32439, 16625, 2478 passed LTC http://tests.stockfishchess.org/tests/view/5e7068eae42a5c3b3ca2e687 LLR: 2.94 (-2.94,2.94) {0.25,1.75} Total: 79318 W: 10463 L: 10064 D: 58791 Ptnml(0-2): 567, 7416, 23359, 7685, 632 closes #2588 Bench: 4952322
diff --git a/src/search.cpp b/src/search.cpp
@@ -1149,7 +1149,7 @@ namespace {
 
           // Decrease reduction if ttMove has been singularly extended (~3 Elo)
           if (singularLMR)
-              r -= 2;
+              r -= 1 + (ttPv && !PvNode);
 
           if (!captureOrPromotion)
           {

Original file line number	Diff line number	Diff line change
`@@ -1149,7 +1149,7 @@ namespace {`
`1149`	`1149`
`1150`	`1150`	`// Decrease reduction if ttMove has been singularly extended (~3 Elo)`
`1151`	`1151`	`if (singularLMR)`
`1152`		`- r -= 2;`
	`1152`	`+ r -= 1 + (ttPv && !PvNode);`
`1153`	`1153`
`1154`	`1154`	`if (!captureOrPromotion)`
`1155`	`1155`	`{`