Less time on first move, -5%.

Bench 2353057

src/search.cpp

@@ -157,7 +157,8 @@ void Search::Worker::start_searching() {
         return;
     }
 
-    main_manager()->tm.init(limits, rootPos.side_to_move(), rootPos.game_ply(), options);
+    main_manager()->tm.init(limits, rootPos.side_to_move(), rootPos.game_ply(), options,
+                            main_manager()->originalPly);
     tt.new_search();
 
     if (rootMoves.empty())

src/search.h

@@ -210,6 +210,7 @@ class SearchManager: public ISearchManager {
             Depth                     depth) const;
 
     Stockfish::TimeManagement tm;
+    int                       originalPly;
     int                       callsCnt;
     std::atomic_bool          ponder;
 

src/thread.cpp

@@ -167,6 +167,7 @@ void ThreadPool::clear() {
     main_manager()->callsCnt                 = 0;
     main_manager()->bestPreviousScore        = VALUE_INFINITE;
     main_manager()->bestPreviousAverageScore = VALUE_INFINITE;
+    main_manager()->originalPly              = -1;
     main_manager()->previousTimeReduction    = 1.0;
     main_manager()->tm.clear();
 }

src/timeman.cpp

@@ -28,6 +28,8 @@
 
 namespace Stockfish {
 
+const static double plyExtra[] = { 0.95, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 };
+
 TimePoint TimeManagement::optimum() const { return optimumTime; }
 TimePoint TimeManagement::maximum() const { return maximumTime; }
 
@@ -47,7 +49,8 @@ void TimeManagement::advance_nodes_time(std::int64_t nodes) {
 void TimeManagement::init(Search::LimitsType& limits,
                           Color               us,
                           int                 ply,
-                          const OptionsMap&   options) {
+                          const OptionsMap&   options,
+                          int&                originalPly) {
     TimePoint npmsec = TimePoint(options["nodestime"]);
 
     // If we have no time, we don't need to fully initialize TM.
@@ -58,6 +61,9 @@ void TimeManagement::init(Search::LimitsType& limits,
     if (limits.time[us] == 0)
         return;
 
+    if (originalPly == -1)
+        originalPly = ply;
+
     TimePoint moveOverhead = TimePoint(options["Move Overhead"]);
 
     // optScale is a percentage of available time to use for the current move.
@@ -106,6 +112,8 @@ void TimeManagement::init(Search::LimitsType& limits,
     {
         // Use extra time with larger increments
         double optExtra = scaledInc < 500 ? 1.0 : 1.13;
+        if (ply - originalPly < 20)
+            optExtra *= plyExtra[(ply - originalPly) / 2];
 
         // Calculate time constants based on current time left.
         double logTimeInSec = std::log10(scaledTime / 1000.0);

src/timeman.h

@@ -36,7 +36,7 @@ struct LimitsType;
 // the maximum available time, the game move number, and other parameters.
 class TimeManagement {
    public:
-    void init(Search::LimitsType& limits, Color us, int ply, const OptionsMap& options);
+    void init(Search::LimitsType& limits, Color us, int ply, const OptionsMap& options, int& originalPly);
 
     TimePoint optimum() const;
     TimePoint maximum() const;