Simplify prior countermove bonus

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 8fdaca7cff046089eefc13365dd97ebf99c3d4b3..e51e2f4dae122310673d40cfced2c5afaea79129 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -616,7 +616,7 @@ namespace {
     // At non-PV nodes we check for an early TT cutoff
     if (  !PvNode
         && !excludedMove
-        && tte->depth() > depth - (tte->bound() == BOUND_EXACT)
+        && tte->depth() > depth
         && ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit
         && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
     {
@@ -745,8 +745,8 @@ namespace {
     }
 
     // Set up the improving flag, which is true if current static evaluation is
-    // bigger than the previous static evaluation at our turn (if we were in 
-    // check at our previous move we look at static evaluaion at move prior to it
+    // bigger than the previous static evaluation at our turn (if we were in
+    // check at our previous move we look at static evaluation at move prior to it
     // and if we were in check at move prior to it flag is set to true) and is
     // false otherwise. The improving flag is used in various pruning heuristics.
     improving =   (ss-2)->staticEval != VALUE_NONE ? ss->staticEval > (ss-2)->staticEval
@@ -1037,7 +1037,7 @@ moves_loop: // When in check, search starts here
               lmrDepth = std::max(lmrDepth, 0);
 
               // Prune moves with negative SEE (~4 Elo)
-              if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth)))
+              if (!pos.see_ge(move, Value(-31 * lmrDepth * lmrDepth)))
                   continue;
           }
       }
@@ -1099,15 +1099,11 @@ moves_loop: // When in check, search starts here
 
               // If we are on a cutNode, reduce it based on depth (negative extension) (~1 Elo)
               else if (cutNode)
-                  extension = depth > 8 && depth < 17 ? -3 : -1;
+                  extension = depth < 17 ? -3 : -1;
 
               // If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
               else if (ttValue <= value)
                   extension = -1;
-
-              // If the eval of ttMove is less than alpha, we reduce it (negative extension) (~1 Elo)
-              else if (ttValue <= alpha)
-                  extension = -1;
           }
 
           // Check extensions (~1 Elo)
@@ -1375,8 +1371,9 @@ moves_loop: // When in check, search starts here
     // Bonus for prior countermove that caused the fail low
     else if (!priorCapture && prevSq != SQ_NONE)
     {
-        int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 113 * depth) + ((ss-1)->moveCount > 12);
+        int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 800) + ((ss-1)->moveCount > 12);
         update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
+        thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << stat_bonus(depth) * bonus / 2;
     }
 
     if (PvNode)
@@ -1413,6 +1410,18 @@ moves_loop: // When in check, search starts here
     assert(PvNode || (alpha == beta - 1));
     assert(depth <= 0);
 
+    // Check if we have an upcoming move that draws by repetition, or
+    // if the opponent had an alternative move earlier to this position.
+    if (   depth < 0
+        && pos.rule50_count() >= 3
+        && alpha < VALUE_DRAW
+        && pos.has_game_cycle(ss->ply))
+    {
+        alpha = value_draw(pos.this_thread());
+        if (alpha >= beta)
+            return alpha;
+    }
+
     Move pv[MAX_PLY+1];
     StateInfo st;
     ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
@@ -1496,10 +1505,10 @@ moves_loop: // When in check, search starts here
             return bestValue;
         }
 
-        if (PvNode && bestValue > alpha)
+        if (bestValue > alpha)
             alpha = bestValue;
 
-        futilityBase = bestValue + 200;
+        futilityBase = std::min(ss->staticEval, bestValue) + 200;
     }
 
     const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
@@ -1608,7 +1617,7 @@ moves_loop: // When in check, search starts here
                 if (PvNode) // Update pv even in fail-high case
                     update_pv(ss->pv, move, (ss+1)->pv);
 
-                if (PvNode && value < beta) // Update alpha here!
+                if (value < beta) // Update alpha here!
                     alpha = value;
                 else
                     break; // Fail high
@@ -1828,7 +1837,7 @@ void MainThread::check_time() {
       return;
 
   // When using nodes, ensure checking rate is not lower than 0.1% of nodes
-  callsCnt = Limits.nodes ? std::min(1024, int(Limits.nodes / 1024)) : 1024;
+  callsCnt = Limits.nodes ? std::min(512, int(Limits.nodes / 1024)) : 512;
 
   static TimePoint lastInfoTime = now();
 
@@ -1845,7 +1854,7 @@ void MainThread::check_time() {
   if (ponder)
       return;
 
-  if (   (Limits.use_time_management() && (elapsed > Time.maximum() - 10 || stopOnPonderhit))
+  if (   (Limits.use_time_management() && (elapsed > Time.maximum() || stopOnPonderhit))
       || (Limits.movetime && elapsed >= Limits.movetime)
       || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
       Threads.stop = true;