Simplify tropism. (#1807)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 34ec48902cfe9986d5c786e11b92fcdc5efc8566..97218baa19f9627cb27ce59948c255e18cef0b81 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -421,7 +421,7 @@ namespace {
     // which are attacked twice in that flank but not defended by our pawns.
     kingFlank = KingFlank[file_of(ksq)];
     b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;
     // which are attacked twice in that flank but not defended by our pawns.
     kingFlank = KingFlank[file_of(ksq)];
     b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;

-    b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
+    b2 = b1 & attackedBy2[Them];

 
     int tropism = popcount(b1) + popcount(b2);
 
 
     int tropism = popcount(b1) + popcount(b2);
 


@@ -480,15 +480,12 @@ namespace {
                      +   4 * tropism
                      - 873 * !pos.count<QUEEN>(Them)
                      -   6 * mg_value(score) / 8
                      +   4 * tropism
                      - 873 * !pos.count<QUEEN>(Them)
                      -   6 * mg_value(score) / 8

+                     +       mg_value(mobility[Them] - mobility[Us])

                      -   30;
 
         // Transform the kingDanger units into a Score, and subtract it from the evaluation
         if (kingDanger > 0)
                      -   30;
 
         // Transform the kingDanger units into a Score, and subtract it from the evaluation
         if (kingDanger > 0)

-        {
-            int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
-            kingDanger = std::max(0, kingDanger + mobilityDanger);

             score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
             score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);

-        }

     }
 
     // Penalty when our king is on a pawnless flank
     }
 
     // Penalty when our king is on a pawnless flank