Smarter time management near stop limit

xoto10 · snicolet · commit 69204f0720bb · 2020-01-12T22:37:24.000+01:00
This patch makes Stockfish search same depth again if > 60% of optimum time is already used, instead of trying the next iteration. The idea is that the next iteration will generally take about the same amount of time as has already been used in total. When we are likely to begin the last iteration, as judged by total time taken so far > 0.6 * optimum time, searching the last depth again instead of increasing the depth still helps the other threads in lazy SMP and prepares better move ordering for the next moves. STC : LLR: 2.95 (-2.94,2.94) {-1.00,3.00} Total: 13436 W: 2695 L: 2558 D: 8183 Ptnml(0-2): 222, 1538, 3087, 1611, 253 https://tests.stockfishchess.org/tests/view/5e1618a761fe5f83a67dd964 LTC : LLR: 2.94 (-2.94,2.94) {0.00,2.00} Total: 32160 W: 4261 L: 4047 D: 23852 Ptnml(0-2): 211, 2988, 9448, 3135, 247 https://tests.stockfishchess.org/tests/view/5e162ca061fe5f83a67dd96d The code was revised as suggested by @vondele for multithreading: STC (8 threads): LLR: 2.95 (-2.94,2.94) {0.00,2.00} Total: 16640 W: 2049 L: 1885 D: 12706 Ptnml(0-2): 119, 1369, 5158, 1557, 108 https://tests.stockfishchess.org/tests/view/5e19826a2cc590e03c3c2f52 LTC (8 threads): LLR: 2.95 (-2.94,2.94) {-1.00,3.00} Total: 16536 W: 2758 L: 2629 D: 11149 Ptnml(0-2): 182, 1758, 4296, 1802, 224 https://tests.stockfishchess.org/tests/view/5e18b91a27dab692fcf9a140 Thanks to those discussing Stockfish lazy SMP on fishcooking which made me try this, and to @vondele for suggestions and doing related tests. See full discussion in the pull request thread: #2482 Bench: 4586187
diff --git a/AUTHORS b/AUTHORS
@@ -91,6 +91,7 @@ Luca Brivio (lucabrivio)
 Lucas Braesch (lucasart)
 Lyudmil Antonov (lantonov)
 Maciej Żenczykowski (zenczykowski)
+Malcolm Campbell (xoto10)
 Mark Tenzer (31m059)
 marotear
 Matthew Lai (matthewlai)
@@ -151,6 +152,12 @@ Tracey Emery (basepr1me)
 Uri Blass (uriblass)
 Vince Negri (cuddlestmonkey)
 
-# Additionally, we acknowledge the authors of fishtest,
-# an essential framework for the development of Stockfish:
+
+# Additionally, we acknowledge the authors and maintainer of fishtest,
+# an amazing and essential framework for the development of Stockfish!
+#
 # https://github.com/glinscott/fishtest/blob/master/AUTHORS
+
+
+
+
diff --git a/src/search.cpp b/src/search.cpp
@@ -393,6 +393,8 @@ void Thread::search() {
   contempt = (us == WHITE ?  make_score(ct, ct / 2)
                           : -make_score(ct, ct / 2));
 
+  int searchAgainCounter = 0;
+
   // Iterative deepening loop until requested to stop or the target depth is reached
   while (   ++rootDepth < MAX_PLY
          && !Threads.stop
@@ -410,6 +412,9 @@ void Thread::search() {
       size_t pvFirst = 0;
       pvLast = 0;
 
+      if (!Threads.increaseDepth)
+         searchAgainCounter++;
+
       // MultiPV loop. We perform a full root search for each PV line
       for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx)
       {
@@ -445,7 +450,7 @@ void Thread::search() {
           int failedHighCnt = 0;
           while (true)
           {
-              Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt);
+              Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
               bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
 
               // Bring the best move to the front. It is critical that sorting
@@ -558,6 +563,11 @@ void Thread::search() {
               else
                   Threads.stop = true;
           }
+          else if (   Threads.increaseDepth
+                   && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6)
+                   Threads.increaseDepth = false;
+          else
+                   Threads.increaseDepth = true;
       }
 
       mainThread->iterValue[iterIdx] = bestValue;
diff --git a/src/thread.cpp b/src/thread.cpp
@@ -179,6 +179,7 @@ void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
   main()->wait_for_search_finished();
 
   main()->stopOnPonderhit = stop = false;
+  increaseDepth = true;
   main()->ponder = ponderMode;
   Search::Limits = limits;
   Search::RootMoves rootMoves;
diff --git a/src/thread.h b/src/thread.h
@@ -109,7 +109,7 @@ struct ThreadPool : public std::vector<Thread*> {
   uint64_t nodes_searched() const { return accumulate(&Thread::nodes); }
   uint64_t tb_hits()        const { return accumulate(&Thread::tbHits); }
 
-  std::atomic_bool stop;
+  std::atomic_bool stop, increaseDepth;
 
 private:
   StateListPtr setupStates;
