Skip quiet moves based on moveCount pruning threshold and history stats

If we can moveCountPrune and next quiet move has negative stats,
then go directly to the next move stage (Bad_Captures).

Reduction formula is tweaked to compensate for the decrease in move count that is used in LMR.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 6847 W: 1276 L: 1123 D: 4448

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 48687 W: 6503 L: 6226 D: 35958

Bench: 5919519

Closes #1036

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 83421272bb033baede512e16db9ebeb078f04f4f..2ea859a26fcf2b9ef4dadfe42d03c0806d082679 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -175,7 +175,7 @@ void MovePicker::score<EVASIONS>() {
 /// left. It picks the move with the biggest value from a list of generated moves
 /// taking care not to return the ttMove if it has already been searched.
 
 /// left. It picks the move with the biggest value from a list of generated moves
 /// taking care not to return the ttMove if it has already been searched.
 

-Move MovePicker::next_move() {
+Move MovePicker::next_move(bool skipQuiets) {

 
   Move move;
 
 
   Move move;
 


@@ -248,9 +248,11 @@ Move MovePicker::next_move() {
       ++stage;
 
   case QUIET:
       ++stage;
 
   case QUIET:

-      while (cur < endMoves)
+      while (    cur < endMoves
+             && (!skipQuiets || cur->value >= VALUE_ZERO))

       {
           move = *cur++;
       {
           move = *cur++;

+

           if (   move != ttMove
               && move != ss->killers[0]
               && move != ss->killers[1]
           if (   move != ttMove
               && move != ss->killers[0]
               && move != ss->killers[1]

diff --git a/src/movepick.h b/src/movepick.h
index e1a2e6df18d3386623ddce7ca77d4023f6a081ec..c19141820e3397804580a06fbc8b02df12e5e7a0 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -95,7 +95,7 @@ public:
   MovePicker(const Position&, Move, Depth, Square);
   MovePicker(const Position&, Move, Depth, Search::Stack*);
 
   MovePicker(const Position&, Move, Depth, Square);
   MovePicker(const Position&, Move, Depth, Search::Stack*);
 

-  Move next_move();
+  Move next_move(bool skipQuiets = false);

 
 private:
   template<GenType> void score();
 
 private:
   template<GenType> void score();

diff --git a/src/search.cpp b/src/search.cpp
index 88af08404d7cdae7c44d381f499763fd9877c119..f07085eda32f6f956cd0a64f3e48acda38cfa2d7 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -163,7 +163,7 @@ void Search::init() {
       for (int d = 1; d < 64; ++d)
           for (int mc = 1; mc < 64; ++mc)
           {
       for (int d = 1; d < 64; ++d)
           for (int mc = 1; mc < 64; ++mc)
           {

-              double r = log(d) * log(mc) / 2;
+              double r = log(d) * log(mc) / 1.95;

 
               Reductions[NonPV][imp][d][mc] = int(std::round(r));
               Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
 
               Reductions[NonPV][imp][d][mc] = int(std::round(r));
               Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);


@@ -542,7 +542,7 @@ namespace {
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;

-    bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
+    bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;

     Piece moved_piece;
     int moveCount, quietCount;
 
     Piece moved_piece;
     int moveCount, quietCount;
 


@@ -829,10 +829,11 @@ moves_loop: // When in check search starts from here
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;

+    skipQuiets = false;

 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
 
     // Step 11. Loop through moves
     // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs

-    while ((move = mp.next_move()) != MOVE_NONE)
+    while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)

     {
       assert(is_ok(move));
 
     {
       assert(is_ok(move));
 


@@ -906,8 +907,10 @@ moves_loop: // When in check search starts from here
               && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= 5000))
           {
               // Move count based pruning
               && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= 5000))
           {
               // Move count based pruning

-              if (moveCountPruning)
+              if (moveCountPruning) {
+                  skipQuiets = true;

                   continue;
                   continue;

+              }

 
               // Reduced depth of the next LMR search
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Reduced depth of the next LMR search
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;