Smarter time management near stop limit

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:
https://github.com/official-stockfish/Stockfish/pull/2482

Bench: 4586187

diff --git a/AUTHORS b/AUTHORS
index 4638b41a391c1cc7286d43c14c715134228b7ce7..33a7a3d559798f72f742f501feeecba4e7a395dc 100644 (file)
--- 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
index 6146bdf6b5ae9ac24f48cb2e3e3ca831bf8f7618..ec9c6b1d0507c77734f92fe8d3a7d067de2334d4 100644 (file)
--- 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
index f55bcb222a6b6045117fad57fe743f0b71f294ae..615d482cafa811a4046eaacf7f21676b28f46ed6 100644 (file)
--- 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
index 4de30edb4ce1e7de38449ff10cbbdd47f268ca0b..aea86fd5c6941312fcf9a5b04ac2c56d2cc67fbd 100644 (file)
--- 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;