Simplify BlockedByPawn to one dimension

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 96a2dc0fb956bcacc142fec4171b2da8c48f317f..448c1191f25f4c92a206fd4d8826c92052cf4fff 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -46,26 +46,26 @@ namespace {
   // Strength of pawn shelter for our king by [distance from edge][rank].
   // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
   constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = {
-    { V( 7), V(76), V(84), V( 38), V( 7), V( 30), V(-19) },
-    { V(-3), V(93), V(52), V(-17), V(12), V(-22), V(-35) },
-    { V(-6), V(83), V(25), V(-24), V(15), V( 22), V(-39) },
-    { V(11), V(83), V(19), V(  8), V(18), V(-21), V(-30) }
+    { V(  7), V(76), V( 84), V( 38), V(  7), V( 30), V(-19) },
+    { V(-13), V(83), V( 42), V(-27), V(  2), V(-32), V(-45) },
+    { V(-26), V(63), V(  5), V(-44), V( -5), V(  2), V(-59) },
+    { V(-19), V(53), V(-11), V(-22), V(-12), V(-51), V(-60) }
   };
 
-  // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
-  // For the unblocked case, RANK_1 = 0 is used when opponent has no pawn on the
-  // given file, or their pawn is behind our king.
-  constexpr Value StormDanger[][4][RANK_NB] = {
-    { { V(25),  V( 79), V(107), V( 51), V( 27) },  // UnBlocked
-      { V(15),  V( 45), V(131), V(  8), V( 25) },
-      { V( 0),  V( 42), V(118), V( 56), V( 27) },
-      { V( 3),  V( 54), V(110), V( 55), V( 26) } },
-    { { V( 0),  V(  0), V( 37), V(  5), V(-48) },  // BlockedByPawn
-      { V( 0),  V(  0), V( 68), V(-12), V( 13) },
-      { V( 0),  V(  0), V(111), V(-25), V( -3) },
-      { V( 0),  V(  0), V(108), V( 14), V( 21) } }
+  // Danger of enemy pawns moving toward our king by [distance from edge][rank].
+  // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn 
+  // is behind our king.
+  constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
+    { V( 25), V( 79), V(107), V( 51), V( 27), V(  0), V(  0) },
+    { V(  5), V( 35), V(121), V( -2), V( 15), V(-10), V(-10) },
+    { V(-20), V( 22), V( 98), V( 36), V(  7), V(-20), V(-20) },
+    { V(-27), V( 24), V( 80), V( 25), V( -4), V(-30), V(-30) }
   };
 
+  // Danger of blocked enemy pawns storming our king, by rank
+  constexpr Value BlockedStorm[RANK_NB] =
+    { V(  0), V(  0), V( 75), V(-10), V(-20), V(-20), V(-20) };
+
   #undef S
   #undef V
 
@@ -208,7 +208,6 @@ Entry* probe(const Position& pos) {
 template<Color Us>
 Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
 
-  enum { UnBlocked, BlockedByPawn };
   constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
   constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
   constexpr Bitboard  BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
@@ -232,10 +231,9 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
       int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
 
       int d = std::min(f, ~f);
-
       safety += ShelterStrength[d][ourRank];
-      safety -= StormDanger[ourRank && (ourRank == theirRank - 1) ? BlockedByPawn : UnBlocked]
-                           [d][theirRank];
+      safety -= (ourRank && (ourRank == theirRank - 1)) ? BlockedStorm[theirRank]
+                                                        : UnblockedStorm[d][theirRank];
   }
 
   return safety;