Make extra time for bestMoveInstability dependent on rootdepth.

This change allocates more base time to moves and makes the additional time added for best move instability dependent on rootdepth.

STC 10+0.1 :
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 19432 W: 1711 L: 1553 D: 16168
Ptnml(0-2): 47, 1250, 6989, 1358, 72
https://tests.stockfishchess.org/tests/view/60b8cd41457376eb8bcaa1ad

LTC 60+0.6 :
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 22480 W: 810 L: 693 D: 20977
Ptnml(0-2): 9, 603, 9902, 714, 12
https://tests.stockfishchess.org/tests/view/60b8e5bf457376eb8bcaa1e6

closes https://github.com/official-stockfish/Stockfish/pull/3526

Bench 4364128

diff --git a/src/search.cpp b/src/search.cpp
index 2c7c6fd671c55e6d9277ca675077f7b4debde2ef..100ddc719e1b474d02c6c0c2df4a022e71e2940c 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -480,8 +480,8 @@ void Thread::search() {
               totBestMoveChanges += th->bestMoveChanges;
               th->bestMoveChanges = 0;
           }
-          double bestMoveInstability = 1 + 2 * totBestMoveChanges / Threads.size();
-
+          double bestMoveInstability = 1.073 + std::max(1.0, 2.25 - 9.9 / rootDepth)
+                                              * totBestMoveChanges / Threads.size();
           double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability;
 
           // Cap used time in case of a single legal move for a better viewer experience in tournaments