Simplification of lazy threshold

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index a00dbf8afb952a8ebe89c4cb9903d56d6a98ebe8..4b9960d530672d2a9113112eade7e20f274e33bc 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -135,19 +135,13 @@ namespace {
       S(118,174), S(119,177), S(123,191), S(128,199) }
   };
 
-  // Outpost[knight/bishop][supported by pawn] contains bonuses for knights and
-  // bishops outposts, bigger if outpost piece is supported by a pawn.
+  // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
+  // pieces if they can reach an outpost square, bigger if that square is
+  // supported by a pawn. If the minor piece occupies an outpost square
+  // then score is doubled.
   const Score Outpost[][2] = {
-    { S(43,11), S(65,20) }, // Knights
-    { S(20, 3), S(29, 8) }  // Bishops
-  };
-
-  // ReachableOutpost[knight/bishop][supported by pawn] contains bonuses for
-  // knights and bishops which can reach an outpost square in one move, bigger
-  // if outpost square is supported by a pawn.
-  const Score ReachableOutpost[][2] = {
-    { S(21, 5), S(35, 8) }, // Knights
-    { S( 8, 0), S(14, 4) }  // Bishops
+    { S(22, 6), S(33, 9) }, // Knight
+    { S( 9, 2), S(14, 4) }  // Bishop
   };
 
   // RookOnFile[semiopen/open] contains bonuses for each rook when there is no
@@ -223,7 +217,7 @@ namespace {
   const int KnightCheck       = 924;
 
   // Threshold for lazy evaluation
-  const Value LazyEval = Value(1500);
+  const Value LazyThreshold = Value(1500);
 
   // eval_init() initializes king and attack bitboards for a given color
   // adding pawn attacks. To be done at the beginning of the evaluation.
@@ -316,12 +310,12 @@ namespace {
             // Bonus for outpost squares
             bb = OutpostRanks & ~ei.pe->pawn_attacks_span(Them);
             if (bb & s)
-                score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
+                score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)] * 2;
             else
             {
                 bb &= b & ~pos.pieces(Us);
                 if (bb)
-                   score += ReachableOutpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
+                   score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
             }
 
             // Bonus when behind a pawn
@@ -798,18 +792,6 @@ namespace {
     return sf;
   }
 
-
-  Value lazy_eval(Value mg, Value eg) {
-
-    if (mg > LazyEval && eg > LazyEval)
-        return  LazyEval + ((mg + eg) / 2 - LazyEval) / 4;
-
-    else if (mg < -LazyEval && eg < -LazyEval)
-        return -LazyEval + ((mg + eg) / 2 + LazyEval) / 4;
-
-    return VALUE_ZERO;
-  }
-
 } // namespace
 
 
@@ -822,6 +804,7 @@ Value Eval::evaluate(const Position& pos) {
   assert(!pos.checkers());
 
   Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
+  Value v;
   EvalInfo ei;
 
   // Probe the material hash table
@@ -841,11 +824,10 @@ Value Eval::evaluate(const Position& pos) {
   ei.pe = Pawns::probe(pos);
   score += ei.pe->pawns_score();
 
-  // We have taken into account all cheap evaluation terms.
-  // If score exceeds a threshold return a lazy evaluation.
-  Value lazy = lazy_eval(mg_value(score), eg_value(score));
-  if (lazy)
-      return pos.side_to_move() == WHITE ? lazy : -lazy;
+  // Early exit if score is high
+  v = (mg_value(score) + eg_value(score)) / 2;
+  if (abs(v) > LazyThreshold)
+     return pos.side_to_move() == WHITE ? v : -v;
 
   // Initialize attack and king safety bitboards
   eval_init<WHITE>(pos, ei);
@@ -880,8 +862,8 @@ Value Eval::evaluate(const Position& pos) {
   ScaleFactor sf = evaluate_scale_factor(pos, ei, eg_value(score));
 
   // Interpolate between a middlegame and a (scaled by 'sf') endgame score
-  Value v =  mg_value(score) * int(ei.me->game_phase())
-           + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
+  v =  mg_value(score) * int(ei.me->game_phase())
+     + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
 
   v /= int(PHASE_MIDGAME);