3.5.6: implement iid - idea from Ethereal (#294)

vshcherbyna · web-flow · commit c0be55099dd4 · 2024-08-24T16:52:49.000+01:00
bench: 1327210
diff --git a/src/search.cpp b/src/search.cpp
@@ -337,6 +337,13 @@ EVAL Search::abSearch(EVAL alpha, EVAL beta, int depth, int ply, bool isNull, bo
         }
     }
 
+    //
+    //  IID
+    //
+
+    if (depth >= 7 && (onPV || cutNode) && (!hashMove || hEntry.m_data.depth + 4 < depth))
+        --depth;
+
     auto legalMoves = 0;
     bestScore = -CHECKMATE_SCORE + ply;
     U8 type = HASH_ALPHA;
diff --git a/src/uci.cpp b/src/uci.cpp
@@ -31,7 +31,7 @@
 #include <iostream>
 #include <sstream>
 
-const std::string VERSION = "3.5.5";
+const std::string VERSION = "3.5.6";
 const std::string ARCHITECTURE = " 64 "
 
 #if _BTYPE==0

Original file line number	Diff line number	Diff line change
`@@ -337,6 +337,13 @@ EVAL Search::abSearch(EVAL alpha, EVAL beta, int depth, int ply, bool isNull, bo`
`337`	`337`	`}`
`338`	`338`	`}`
`339`	`339`
	`340`	`+ //`
	`341`	`+ // IID`
	`342`	`+ //`
	`343`	`+`
	`344`	`+ if (depth >= 7 && (onPV \|\| cutNode) && (!hashMove \|\| hEntry.m_data.depth + 4 < depth))`
	`345`	`+ --depth;`
	`346`	`+`
`340`	`347`	`auto legalMoves = 0;`
`341`	`348`	`bestScore = -CHECKMATE_SCORE + ply;`
`342`	`349`	`U8 type = HASH_ALPHA;`