Skip skipping thread scheme (#1972)

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 9165468ae0590e82740f53c7296f7aef9f7ce643..cf934fc92c15434066828c72498f87f0d7f8e340 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -61,10 +61,6 @@ namespace {
   // Different node types, used as a template parameter
   enum NodeType { NonPV, PV };
 
-  // Sizes and phases of the skip-blocks, used for distributing search depths across the threads
-  constexpr int SkipSize[]  = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
-  constexpr int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
-
   // Razor and futility margins
   constexpr int RazorMargin = 600;
   Value futility_margin(Depth d, bool improving) {
@@ -297,7 +293,6 @@ void Thread::search() {
   MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
   double timeReduction = 1.0;
   Color us = rootPos.side_to_move();
-  bool failedLow;
 
   std::memset(ss-7, 0, 10 * sizeof(Stack));
   for (int i = 7; i > 0; i--)
@@ -308,7 +303,7 @@ void Thread::search() {
   beta = VALUE_INFINITE;
 
   if (mainThread)
-      mainThread->bestMoveChanges = 0, failedLow = false;
+      mainThread->bestMoveChanges = 0;
 
   size_t multiPV = Options["MultiPV"];
   Skill skill(Options["Skill Level"]);
@@ -339,17 +334,9 @@ void Thread::search() {
          && !Threads.stop
          && !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth))
   {
-      // Distribute search depths across the helper threads
-      if (idx > 0)
-      {
-          int i = (idx - 1) % 20;
-          if (((rootDepth / ONE_PLY + SkipPhase[i]) / SkipSize[i]) % 2)
-              continue;  // Retry with an incremented rootDepth
-      }
-
       // Age out PV variability metric
       if (mainThread)
-          mainThread->bestMoveChanges *= 0.517, failedLow = false;
+          mainThread->bestMoveChanges *= 0.517;
 
       // Save the last iteration's scores before first PV line is searched and
       // all the move scores except the (new) PV are set to -VALUE_INFINITE.
@@ -429,7 +416,6 @@ void Thread::search() {
                   if (mainThread)
                   {
                       failedHighCnt = 0;
-                      failedLow = true;
                       mainThread->stopOnPonderhit = false;
                   }
               }
@@ -481,19 +467,19 @@ void Thread::search() {
           && !Threads.stop
           && !mainThread->stopOnPonderhit)
       {
-          double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0;
+          double fallingEval = (306 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
           fallingEval        = std::max(0.5, std::min(1.5, fallingEval));
 
           // If the bestMove is stable over several iterations, reduce time accordingly
           timeReduction = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0;
+          double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
 
           // Use part of the gained time from a previous stable move for the current move
           double bestMoveInstability = 1.0 + mainThread->bestMoveChanges;
-          bestMoveInstability *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
 
           // Stop the search if we have only one legal move, or if available time elapsed
           if (   rootMoves.size() == 1
-              || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval)
+              || Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability)
           {
               // If we are allowed to ponder do not stop the search now but
               // keep pondering until the GUI sends "ponderhit" or "stop".