Drop OnlyMoveExt PV-condition from 8 plies to 6 plies

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 7eb04308b4c3bbd6c72247a6d920927ffc91b9e5..95d8be98bc858cad282f233abf5dad0b011eb3fc 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1139,9 +1139,8 @@ namespace {
         ttMove = ss[ply].pv[ply];
         tte = TT.retrieve(pos.get_key());
 
-        // Following assert could fail, for instance when we have
-        // moveCount == 0 we return without saving a TT entry.
-        /* assert(tte); */
+        // If tte->move() != MOVE_NONE then it equals ttMove
+        assert(!(tte && tte->move()) || tte->move() == ttMove);
     }
 
     // Initialize a MovePicker object for the current position, and prepare
@@ -1170,9 +1169,7 @@ namespace {
       // To verify this we do a reduced search on all the other moves but the ttMove,
       // if result is lower then TT value minus a margin then we assume ttMove is the
       // only one playable. It is a kind of relaxed single reply extension.
-      // Note that could be ttMove != tte->move() due to IID, so we always use tte->move()
-      // to avoid aliases when we probe tte->depth() and tte->type()
-      if (   depth >= 8 * OnePly
+      if (   depth >= 6 * OnePly
           && tte
           && move == tte->move()
           && ext < OnePly
@@ -1183,7 +1180,7 @@ namespace {
 
           if (abs(ttValue) < VALUE_KNOWN_WIN)
           {
-              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, ttMove);
+              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
 
               // If search result is well below the foreseen score of the ttMove then we
               // assume ttMove is the only one realistically playable and we extend it.
@@ -1476,8 +1473,6 @@ namespace {
       // To verify this we do a reduced search on all the other moves but the ttMove,
       // if result is lower then TT value minus a margin then we assume ttMove is the
       // only one playable. It is a kind of relaxed single reply extension.
-      // Note that could be ttMove != tte->move() due to IID, so we always use tte->move()
-      // to avoid aliases when we probe tte->depth() and tte->type()
       if (   depth >= 8 * OnePly
           && tte
           && move == tte->move()
@@ -1490,7 +1485,7 @@ namespace {
 
           if (abs(ttValue) < VALUE_KNOWN_WIN)
           {
-              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, ttMove);
+              Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
 
               // If search result is well below the foreseen score of the ttMove then we
               // assume ttMove is the only one realistically playable and we extend it.