Remove SlowMover Option

The SlowMover option allows users to modify the timeLeft variant, impacting the
engine's time management. However, this feature, while theoretically flexible,
doesn't offer substantial benefits. Instead, it introduces the risk of
non-experienced users altering values without a clear understanding of the
effects, potentially leading to a weaker engine.

The vast majority of SF users don't use it anyway, and based on tests conducted
by fauzi several months ago suggest that changing it would only lose Elo.

Examples:
https://tests.stockfishchess.org/tests/view/651f309bac57711436726bba
https://tests.stockfishchess.org/tests/view/651fea29ac57711436727d85
https://tests.stockfishchess.org/tests/view/65257c343125598fc7eb68a1
https://tests.stockfishchess.org/tests/view/652296c83125598fc7eb2ad7
Tune:
https://tests.stockfishchess.org/tests/view/652a70313125598fc7ebd706
(keeping the value at 100, zz2)

closes https://github.com/official-stockfish/Stockfish/pull/4917

No functional change

diff --git a/src/timeman.cpp b/src/timeman.cpp
index 1253d434672709094cb7496dea0b37f08dc02fb5..9ff422fe9663f3f6b601a129e4f4a8e4ae0f1e7c 100644 (file)
--- a/src/timeman.cpp
+++ b/src/timeman.cpp
@@ -42,7 +42,6 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
         return;
 
     TimePoint moveOverhead = TimePoint(Options["Move Overhead"]);
-    TimePoint slowMover    = TimePoint(Options["Slow Mover"]);
     TimePoint npmsec       = TimePoint(Options["nodestime"]);
 
     // optScale is a percentage of available time to use for the current move.
@@ -78,10 +77,6 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
     double optConstant = std::min(0.00335 + 0.0003 * std::log10(limits.time[us] / 1000.0), 0.0048);
     double maxConstant = std::max(3.6 + 3.0 * std::log10(limits.time[us] / 1000.0), 2.7);
 
-    // A user may scale time usage by setting UCI option "Slow Mover"
-    // Default is 100 and changing this value will probably lose elo.
-    timeLeft = slowMover * timeLeft / 100;
-
     // x basetime (+ z increment)
     // If there is a healthy increment, timeLeft can exceed actual available
     // game time for the current move, so also cap to 20% of available game time.

diff --git a/src/ucioption.cpp b/src/ucioption.cpp
index d0db1c76dd22967a1215b9b6bffd54511816da6b..233602ca153edc27f5b38ccb7348d48e758fafbe 100644 (file)
--- a/src/ucioption.cpp
+++ b/src/ucioption.cpp
@@ -73,7 +73,6 @@ void init(OptionsMap& o) {
     o["MultiPV"] << Option(1, 1, 500);
     o["Skill Level"] << Option(20, 0, 20);
     o["Move Overhead"] << Option(10, 0, 5000);
-    o["Slow Mover"] << Option(100, 10, 1000);
     o["nodestime"] << Option(0, 0, 10000);
     o["UCI_Chess960"] << Option(false);
     o["UCI_AnalyseMode"] << Option(false);