Simplify bestvalue update formula

FauziAkram · Disservin · commit 93b966829bd7 · 2025-02-24T19:16:26.000+01:00
Passed STC: LLR: 2.95 (-2.94,2.94) <-1.75,0.25> Total: 124960 W: 32598 L: 32472 D: 59890 Ptnml(0-2): 480, 14852, 31694, 14970, 484 https://tests.stockfishchess.org/tests/view/67b348bae00eea114cdba37d Passed LTC: LLR: 2.94 (-2.94,2.94) <-1.75,0.25> Total: 150306 W: 38220 L: 38132 D: 73954 Ptnml(0-2): 98, 16430, 42005, 16526, 94 https://tests.stockfishchess.org/tests/view/67b5e37918a66624a7a3f751 closes #5898 Bench: 2146010
diff --git a/src/search.cpp b/src/search.cpp
@@ -1720,8 +1720,8 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
         return mated_in(ss->ply);  // Plies to mate from the root
     }
 
-    if (!is_decisive(bestValue) && bestValue >= beta)
-        bestValue = (3 * bestValue + beta) / 4;
+    if (!is_decisive(bestValue) && bestValue > beta)
+        bestValue = (bestValue + beta) / 2;
 
     // Save gathered info in transposition table. The static evaluation
     // is saved as it was before adjustment by correction history.

Original file line number	Diff line number	Diff line change
`@@ -1720,8 +1720,8 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)`
`1720`	`1720`	`return mated_in(ss->ply); // Plies to mate from the root`
`1721`	`1721`	`}`
`1722`	`1722`
`1723`		`- if (!is_decisive(bestValue) && bestValue >= beta)`
`1724`		`- bestValue = (3 * bestValue + beta) / 4;`
	`1723`	`+ if (!is_decisive(bestValue) && bestValue > beta)`
	`1724`	`+ bestValue = (bestValue + beta) / 2;`
`1725`	`1725`
`1726`	`1726`	`// Save gathered info in transposition table. The static evaluation`
`1727`	`1727`	`// is saved as it was before adjustment by correction history.`