Symmetric king safety

Retire current asymmetric king evaluation
and use a much simpler symmetric one.

As a side effect retire the infamous
'Aggressiveness' and 'Cowardice' UCI
options.

Tested in no-regression mode,

Passed both STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 33855 W: 5863 L: 5764 D: 22228

And LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 40571 W: 5852 L: 5760 D: 28959

bench: 8321835

src/evaluate.cpp

@@ -90,8 +90,8 @@ namespace {
   }
 
   // Evaluation weights, initialized from UCI options
-  enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
+  enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
-  struct Weight { int mg, eg; } Weights[6];
+  struct Weight { int mg, eg; } Weights[5];
 
   typedef Value V;
   #define S(mg, eg) make_score(mg, eg)
@@ -103,7 +103,7 @@ namespace {
   //
   // Values modified by Joona Kiiski
   const Score WeightsInternal[] = {
-    S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
+    S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(289, 0)
   };
 
   // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
@@ -202,9 +202,9 @@ namespace {
   const int BishopCheck       = 2;
   const int KnightCheck       = 3;
 
-  // KingDanger[Color][attackUnits] contains the actual king danger weighted
+  // KingDanger[attackUnits] contains the actual king danger weighted
-  // scores, indexed by color and by a calculated integer number.
+  // scores, indexed by a calculated integer number.
-  Score KingDanger[COLOR_NB][128];
+  Score KingDanger[128];
 
 
   // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
@@ -501,7 +501,7 @@ namespace {
 
         // Finally, extract the king danger score from the KingDanger[]
         // array and subtract the score from evaluation.
-        score -= KingDanger[Us == Search::RootColor][attackUnits];
+        score -= KingDanger[attackUnits];
     }
 
     if (Trace)
@@ -902,8 +902,7 @@ namespace Eval {
     Weights[PawnStructure]  = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
     Weights[PassedPawns]    = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
     Weights[Space]          = weight_option("Space", "Space", WeightsInternal[Space]);
-    Weights[KingDangerUs]   = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
+    Weights[KingSafety]     = weight_option("King Safety", "King Safety", WeightsInternal[KingSafety]);
-    Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
 
     const double MaxSlope = 30;
     const double Peak = 1280;
@@ -911,9 +910,7 @@ namespace Eval {
     for (int t = 0, i = 1; i < 100; ++i)
     {
         t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
-
+        KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);
-        KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
-        KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
     }
   }
 

src/search.cpp

@@ -42,7 +42,6 @@ namespace Search {
   LimitsType Limits;
   std::vector<RootMove> RootMoves;
   Position RootPos;
-  Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
 }
@@ -182,12 +181,11 @@ void Search::think() {
 
   static PolyglotBook book; // Defined static to initialize the PRNG only once
 
-  RootColor = RootPos.side_to_move();
+  TimeMgr.init(Limits, RootPos.game_ply(), 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[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf);
-  DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
+  DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf);
 
   if (RootMoves.empty())
   {
@@ -216,8 +214,8 @@ void Search::think() {
       log << "\nSearching: "  << RootPos.fen()
           << "\ninfinite: "   << Limits.infinite
           << " ponder: "      << Limits.ponder
-          << " time: "        << Limits.time[RootColor]
+          << " time: "        << Limits.time[RootPos.side_to_move()]
-          << " increment: "   << Limits.inc[RootColor]
+          << " increment: "   << Limits.inc[RootPos.side_to_move()]
           << " moves to go: " << Limits.movestogo
           << "\n" << std::endl;
   }

src/search.h

@@ -101,7 +101,6 @@ extern volatile SignalsType Signals;
 extern LimitsType Limits;
 extern std::vector<RootMove> RootMoves;
 extern Position RootPos;
-extern Color RootColor;
 extern Time::point SearchTime;
 extern StateStackPtr SetupStates;
 

src/uci.cpp

@@ -195,11 +195,6 @@ void UCI::loop(int argc, char* argv[]) {
                     << "\n"       << Options
                     << "\nuciok"  << sync_endl;
 
-      else if (token == "eval")
-      {
-          Search::RootColor = pos.side_to_move(); // Ensure it is set
-          sync_cout << Eval::trace(pos) << sync_endl;
-      }
       else if (token == "ucinewgame") TT.clear();
       else if (token == "go")         go(pos, is);
       else if (token == "position")   position(pos, is);
@@ -207,6 +202,7 @@ void UCI::loop(int argc, char* argv[]) {
       else if (token == "flip")       pos.flip();
       else if (token == "bench")      benchmark(pos, is);
       else if (token == "d")          sync_cout << pos.pretty() << sync_endl;
+      else if (token == "eval")       sync_cout << Eval::trace(pos) << sync_endl;
       else if (token == "isready")    sync_cout << "readyok" << sync_endl;
       else
           sync_cout << "Unknown command: " << cmd << sync_endl;

src/ucioption.cpp

@@ -67,8 +67,7 @@ void init(OptionsMap& o) {
   o["Passed Pawns (Midgame)"]   << Option(100, 0, 200, on_eval);
   o["Passed Pawns (Endgame)"]   << Option(100, 0, 200, on_eval);
   o["Space"]                    << Option(100, 0, 200, on_eval);
-  o["Aggressiveness"]           << Option(100, 0, 200, on_eval);
+  o["King Safety"]              << Option(100, 0, 200, on_eval);
-  o["Cowardice"]                << Option(100, 0, 200, on_eval);
   o["Min Split Depth"]          << Option(0, 0, 12, on_threads);
   o["Threads"]                  << Option(1, 1, MAX_THREADS, on_threads);
   o["Hash"]                     << Option(32, 1, 16384, on_hash_size);