Less pruning in qsearch

unaiic · vondele · commit 0e1f734b05ee · 2020-09-04T07:55:41.000+02:00
do not prune moves that give discovery checks, even if with negative SSE. STC https://tests.stockfishchess.org/tests/view/5f4cb5e8ba100690c5cc5d25 LLR: 2.96 (-2.94,2.94) {-0.25,1.25} Total: 91328 W: 9940 L: 9667 D: 71721 Ptnml(0-2): 491, 7345, 29693, 7670, 465 LTC https://tests.stockfishchess.org/tests/view/5f4dbc2eba100690c5cc5dac LLR: 2.97 (-2.94,2.94) {0.25,1.25} Total: 52448 W: 2799 L: 2586 D: 47063 Ptnml(0-2): 53, 2220, 21459, 2445, 47 closes #3098 bench: 4031192
diff --git a/src/search.cpp b/src/search.cpp
@@ -1564,7 +1564,9 @@ namespace {
       }
 
       // Do not search moves with negative SEE values
-      if (!ss->inCheck && !pos.see_ge(move))
+      if (   !ss->inCheck
+          && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))
+          && !pos.see_ge(move))
           continue;
 
       // Speculative prefetch as early as possible

Original file line number	Diff line number	Diff line change
`@@ -1564,7 +1564,9 @@ namespace {`
`1564`	`1564`	`}`
`1565`	`1565`
`1566`	`1566`	`// Do not search moves with negative SEE values`
`1567`		`- if (!ss->inCheck && !pos.see_ge(move))`
	`1567`	`+ if ( !ss->inCheck`
	`1568`	`+ && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))`
	`1569`	`+ && !pos.see_ge(move))`
`1568`	`1570`	`continue;`
`1569`	`1571`
`1570`	`1572`	`// Speculative prefetch as early as possible`