Rise contempt when in advantage

This is a very discussed patch with many
argumentations pro and against. The fact is
it passed both STC:

LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 16305 W: 3001 L: 2855 D: 10449

And LTC
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 34273 W: 5180 L: 4931 D: 24162

Although it is true that a correct test should
include foreign engines, we commit it anyhow so
people can test it out in the wild, under broader
conditions.

bench: 7384368

diff --git a/src/search.cpp b/src/search.cpp
index 2ae1c368c4e76b62c17f8e275b27ed32a5f5f1d8..03af5d66d96bc393bb1106dd56694d32f560a48a 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -45,6 +45,7 @@ namespace Search {
   Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
+  Value Contempt[2]; // [bestValue > VALUE_DRAW]
 }
 
 using std::string;
@@ -185,9 +186,8 @@ void Search::think() {
   RootColor = RootPos.side_to_move();
   TimeMgr.init(Limits, RootPos.game_ply(), RootColor);
 
-  int cf = Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
-  DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
-  DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
+  Contempt[0] =  Options["Contempt Factor"] * PawnValueEg / 100; // From centipawns
+  Contempt[1] = (Options["Contempt Factor"] + 12) * PawnValueEg / 100;
 
   if (RootMoves.empty())
   {
@@ -339,6 +339,9 @@ namespace {
             {
                 bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY, false);
 
+                DrawValue[ RootColor] = VALUE_DRAW - Contempt[bestValue > VALUE_DRAW];
+                DrawValue[~RootColor] = VALUE_DRAW + Contempt[bestValue > VALUE_DRAW];
+
                 // Bring the best move to the front. It is critical that sorting
                 // is done with a stable algorithm because all the values but the
                 // first and eventually the new best one are set to -VALUE_INFINITE