Revert "Revert "Shuffle detection #2064""
authorSteinar H. Gunderson <sgunderson@bigfoot.com>
Thu, 18 Apr 2019 20:10:43 +0000 (22:10 +0200)
committerSteinar H. Gunderson <sgunderson@bigfoot.com>
Thu, 18 Apr 2019 20:10:43 +0000 (22:10 +0200)
This reverts commit 5928cb2b300baafb040495ce41f9a5f42132d141.

src/search.cpp

index 15e88ca4f2746939bd3c3e25b04ed15ff11b3824..95b14021c4e51bc7f7d8ad3d89686fd4ee8739c2 100644 (file)
@@ -607,6 +607,15 @@ namespace {
             : ttHit    ? tte->move() : MOVE_NONE;
     ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY);
 
+    // if position has been searched at higher depths and we are shuffling, return value_draw
+    if (pos.rule50_count() > 36
+        && ss->ply > 36
+        && depth < 3 * ONE_PLY
+        && ttHit
+        && tte->depth() > depth
+        && pos.count<PAWN>() > 0)
+        return VALUE_DRAW;
+
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && ttHit
@@ -924,6 +933,10 @@ moves_loop: // When in check, search starts from here
                && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
           extension = ONE_PLY;
 
+      // Shuffle extension
+      else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode)
+          extension = ONE_PLY;
+
       // Castling extension
       else if (type_of(move) == CASTLING)
           extension = ONE_PLY;