Simplify late countermove bonus condition

dubslow · vondele · commit 085cace4574b · 2023-02-18T13:34:40.000+01:00
STC: https://tests.stockfishchess.org/tests/view/63d53ac6a67dd929a555e1e2 LLR: 2.95 (-2.94,2.94) <-1.75,0.25> Total: 216096 W: 56862 L: 56839 D: 102395 Ptnml(0-2): 648, 24033, 58650, 24082, 635 LTC: https://tests.stockfishchess.org/tests/view/63d7f9a6a67dd929a5565991 LLR: 2.95 (-2.94,2.94) <-1.75,0.25> Total: 808512 W: 214060 L: 214610 D: 379842 Ptnml(0-2): 301, 79448, 245293, 78928, 286 closes #4392 Bench: 4283297
diff --git a/src/search.cpp b/src/search.cpp
@@ -1371,11 +1371,10 @@ namespace {
                          quietsSearched, quietCount, capturesSearched, captureCount, depth);
 
     // Bonus for prior countermove that caused the fail low
-    else if (   (depth >= 5 || PvNode || bestValue < alpha - 65 * depth)
-             && !priorCapture)
+    else if (!priorCapture)
     {
         // Extra bonuses for PV/Cut nodes or bad fail lows
-        int bonus = 1 + (PvNode || cutNode) + (bestValue < alpha - 88 * depth);
+        int bonus = (depth > 4) + (PvNode || cutNode) + (bestValue < alpha - 88 * depth);
         update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
     }
 

Original file line number	Diff line number	Diff line change
`@@ -1371,11 +1371,10 @@ namespace {`
`1371`	`1371`	`quietsSearched, quietCount, capturesSearched, captureCount, depth);`
`1372`	`1372`
`1373`	`1373`	`// Bonus for prior countermove that caused the fail low`
`1374`		`- else if ( (depth >= 5 \|\| PvNode \|\| bestValue < alpha - 65 * depth)`
`1375`		`- && !priorCapture)`
	`1374`	`+ else if (!priorCapture)`
`1376`	`1375`	`{`
`1377`	`1376`	`// Extra bonuses for PV/Cut nodes or bad fail lows`
`1378`		`- int bonus = 1 + (PvNode \|\| cutNode) + (bestValue < alpha - 88 * depth);`
	`1377`	`+ int bonus = (depth > 4) + (PvNode \|\| cutNode) + (bestValue < alpha - 88 * depth);`
`1379`	`1378`	`update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);`
`1380`	`1379`	`}`
`1381`	`1380`