Further simplify skipping of plies with threads

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index b75870ff5021968f66d0e0a0aa02271a310cec00..932aaf4dc1a579cbc9bf5f9a41d4a3124d7097ab 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -132,35 +132,6 @@ namespace {
     Move pv[3];
   };
 
-  // Set of rows with half bits set to 1 and half to 0. It is used to allocate
-  // the search depths across the threads.
-  typedef std::vector<int> Row;
-
-  const Row HalfDensity[] = {
-    {0, 1},
-    {1, 0},
-    {0, 0, 1, 1},
-    {0, 1, 1, 0},
-    {1, 1, 0, 0},
-    {1, 0, 0, 1},
-    {0, 0, 0, 1, 1, 1},
-    {0, 0, 1, 1, 1, 0},
-    {0, 1, 1, 1, 0, 0},
-    {1, 1, 1, 0, 0, 0},
-    {1, 1, 0, 0, 0, 1},
-    {1, 0, 0, 0, 1, 1},
-    {0, 0, 0, 0, 1, 1, 1, 1},
-    {0, 0, 0, 1, 1, 1, 1, 0},
-    {0, 0, 1, 1, 1, 1, 0 ,0},
-    {0, 1, 1, 1, 1, 0, 0 ,0},
-    {1, 1, 1, 1, 0, 0, 0 ,0},
-    {1, 1, 1, 0, 0, 0, 0 ,1},
-    {1, 1, 0, 0, 0, 0, 1 ,1},
-    {1, 0, 0, 0, 0, 1, 1 ,1},
-  };
-
-  const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
-
   EasyMoveManager EasyMove;
   Value DrawValue[COLOR_NB];
 
@@ -337,6 +308,9 @@ void MainThread::search() {
   std::cout << sync_endl;
 }
 
+// Sizes and phases of the skip-blocks, used for distributing search depths across the threads.
+static int skipsize[20] = {1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4};
+static int phase   [20] = {0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7};
 
 // Thread::search() is the main iterative deepening loop. It calls search()
 // repeatedly with increasing depth until the allocated thinking time has been
@@ -374,19 +348,16 @@ void Thread::search() {
 
   multiPV = std::min(multiPV, rootMoves.size());
 
+  int hIdx = (idx - 1) % 20; // helper index, cycle after 20 threads
+
   // Iterative deepening loop until requested to stop or the target depth is reached
   while (   (rootDepth += ONE_PLY) < DEPTH_MAX
          && !Signals.stop
          && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth))
   {
-      // Set up the new depths for the helper threads skipping on average every
-      // 2nd ply (using a half-density matrix).
-      if (!mainThread)
-      {
-          const Row& row = HalfDensity[(idx - 1) % HalfDensitySize];
-          if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()])
-             continue;
-      }
+      // skip half of the plies in blocks depending on game ply and helper index.
+      if (idx && ((rootDepth / ONE_PLY + rootPos.game_ply() + phase[hIdx]) / skipsize[hIdx]) % 2)
+          continue;
 
       // Age out PV variability metric
       if (mainThread)
@@ -423,7 +394,7 @@ void Thread::search() {
               // search the already searched PV lines are preserved.
               std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end());
 
-              // If search has been stopped, break immediately. Sorting and
+              // If search has been stopped, we break immediately. Sorting and
               // writing PV back to TT is safe because RootMoves is still
               // valid, although it refers to the previous iteration.
               if (Signals.stop)
@@ -505,7 +476,7 @@ void Thread::search() {
 
               bool doEasyMove =   rootMoves[0].pv[0] == easyMove
                                && mainThread->bestMoveChanges < 0.03
-                               && Time.elapsed() > Time.optimum() * 5 / 42;
+                               && Time.elapsed() > Time.optimum() * 5 / 44;
 
               if (   rootMoves.size() == 1
                   || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628
@@ -564,7 +535,7 @@ namespace {
     Key posKey;
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
-    Value bestValue, value, ttValue, eval, nullValue;
+    Value bestValue, value, ttValue, eval;
     bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
     Piece moved_piece;
@@ -657,7 +628,7 @@ namespace {
                     update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
             }
             // Penalty for a quiet ttMove that fails low
-            else if (ttValue < alpha && !pos.capture_or_promotion(ttMove))
+            else if (!pos.capture_or_promotion(ttMove))
             {
                 Value penalty = -stat_bonus(depth + ONE_PLY);
                 thisThread->history.update(pos.side_to_move(), ttMove, penalty);
@@ -733,7 +704,6 @@ namespace {
     // Step 6. Razoring (skipped when in check)
     if (   !PvNode
         &&  depth < 4 * ONE_PLY
-        &&  ttMove == MOVE_NONE
         &&  eval + razor_margin[depth / ONE_PLY] <= alpha)
     {
         if (depth <= ONE_PLY)
@@ -768,8 +738,8 @@ namespace {
         Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
 
         pos.do_null_move(st);
-        nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1)
-                                      : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
+        Value nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1)
+                                            : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
         pos.undo_null_move();
 
         if (nullValue >= beta)
@@ -924,7 +894,7 @@ moves_loop: // When in check search starts from here
       {
           if (   !captureOrPromotion
               && !givesCheck
-              && !pos.advanced_pawn_push(move))
+              && (!pos.advanced_pawn_push(move) || pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 5000))
           {
               // Move count based pruning
               if (moveCountPruning)