SE depth scaling using the previous depth

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cd38e62920f4dc37b00b0b7ca43c7742f9232056..4a41a8b0b09e275284424c37bed3d8f2edcb69d3 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -238,6 +238,9 @@ void MainThread::search() {
   bestPreviousScore = bestThread->rootMoves[0].score;
   bestPreviousAverageScore = bestThread->rootMoves[0].averageScore;
 
+  for (Thread* th : Threads)
+    th->previousDepth = bestThread->completedDepth;
+
   // Send again PV info if we have a new best thread
   if (bestThread != this)
       sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
@@ -603,6 +606,7 @@ namespace {
     (ss+1)->ttPv         = false;
     (ss+1)->excludedMove = bestMove = MOVE_NONE;
     (ss+2)->killers[0]   = (ss+2)->killers[1] = MOVE_NONE;
+    (ss+2)->cutoffCnt    = 0;
     ss->doubleExtensions = (ss-1)->doubleExtensions;
     ss->depth            = depth;
     Square prevSq        = to_sq((ss-1)->currentMove);
@@ -1060,7 +1064,7 @@ moves_loop: // When in check, search starts here
           // a reduced search on all the other moves but the ttMove and if the
           // result is lower than ttValue minus a margin, then we will extend the ttMove.
           if (   !rootNode
-              &&  depth >= 4 + 2 * (PvNode && tte->is_pv())
+              &&  depth >= 4 - (thisThread->previousDepth > 27) + 2 * (PvNode && tte->is_pv())
               &&  move == ttMove
               && !excludedMove // Avoid recursive singular search
            /* &&  ttValue != VALUE_NONE Already implicit in the next condition */
@@ -1175,6 +1179,10 @@ moves_loop: // When in check, search starts here
           if (PvNode)
               r -= 1 + 15 / ( 3 + depth );
 
+          // Increase reduction if next ply has a lot of fail high else reset count to 0
+          if ((ss+1)->cutoffCnt > 3 && !PvNode)
+              r++;
+
           ss->statScore =  thisThread->mainHistory[us][from_to(move)]
                          + (*contHist[0])[movedPiece][to_sq(move)]
                          + (*contHist[1])[movedPiece][to_sq(move)]
@@ -1295,14 +1303,29 @@ moves_loop: // When in check, search starts here
                   update_pv(ss->pv, move, (ss+1)->pv);
 
               if (PvNode && value < beta) // Update alpha! Always alpha < beta
+              {
                   alpha = value;
+
+                  // Reduce other moves if we have found at least one score improvement
+                  if (   depth > 2
+                      && depth < 7
+                      && beta  <  VALUE_KNOWN_WIN
+                      && alpha > -VALUE_KNOWN_WIN)
+                     depth -= 1;
+
+                  assert(depth > 0);
+              }
               else
               {
+                  ss->cutoffCnt++;
                   assert(value >= beta); // Fail high
                   break;
               }
           }
       }
+      else
+         ss->cutoffCnt = 0;
+
 
       // If the move is worse than some previously searched move, remember it to update its stats later
       if (move != bestMove)