Prefer names to numbers in storm code

Also replaces some tabs with spaces and
change StormDanger order to reflect
ShelterWeakness one.

No functional change.

Author: mcostalba

src/pawns.cpp

@@ -60,32 +60,31 @@ namespace {
   // Unsupported pawn penalty
   const Score UnsupportedPawnPenalty = S(20, 10);
 
-  // Weakness of our pawn shelter in front of the king indexed by [file pairs (a/h,b/g,c/f,d/e)][rank]
+  // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
   const Value ShelterWeakness[][RANK_NB] = {
   { V(101), V(10), V(24), V(68), V(90), V( 95), V(102) },
   { V(105), V( 1), V(30), V(76), V(95), V(100), V(105) },
   { V( 99), V( 0), V(32), V(72), V(92), V(101), V(100) },
   { V( 94), V( 1), V(31), V(68), V(89), V( 98), V(106) } };
 
-  // Danger of enemy pawns moving toward our king indexed by
-  // [file pairs (a/h,b/g,c/f,d/e)][no friendly pawn | pawn unblocked | pawn blocked by pawn| pawn blocked by king][rank of enemy pawn]
+  // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
   const Value StormDanger[][4][RANK_NB] = {
   { { V( 0),  V(  61), V( 128), V(47), V(27) },
-    { V(25),  V(  33), V(  95), V(39), V(21) },
-    { V( 0),  V(   0), V(  80), V(14), V( 8) },
-    { V( 0),  V(-300), V(-300), V(54), V(23) } },
-  { { V( 0),  V(  66), V( 131), V(49), V(27) },
+    { V( 0),  V(  66), V( 131), V(49), V(27) },
+    { V( 0),  V(  62), V( 126), V(52), V(23) },
+    { V( 0),  V(  63), V( 128), V(52), V(26) } },
+  { { V(25),  V(  33), V(  95), V(39), V(21) },
     { V(24),  V(  33), V(  97), V(42), V(22) },
-    { V( 0),  V(   0), V( 163), V(28), V(12) },
-    { V( 0),  V(  67), V( 128), V(46), V(24) }	},
-  { { V( 0),  V(  62), V( 126), V(52), V(23) },
     { V(24),  V(  33), V(  93), V(35), V(23) },
+    { V(26),  V(  27), V(  96), V(37), V(22) } },
+  { { V( 0),  V(   0), V(  80), V(14), V( 8) },
+    { V( 0),  V(   0), V( 163), V(28), V(12) },
     { V( 0),  V(   0), V( 163), V(25), V(15) },
-    { V( 0),  V(  64), V( 130), V(50), V(29) }	},
-  { { V( 0),  V(  63), V( 128), V(52), V(26) },
-    { V(26),  V(  27), V(  96), V(37), V(22) },
-    { V( 0),  V(   0), V( 161), V(24), V(14) },
-    { V( 0),  V(  63), V( 127), V(51), V(24) }	} };
+    { V( 0),  V(   0), V( 161), V(24), V(14) } },
+  { { V( 0),  V(-300), V(-300), V(54), V(23) },
+    { V( 0),  V(  67), V( 128), V(46), V(24) },
+    { V( 0),  V(  64), V( 130), V(50), V(29) },
+    { V( 0),  V(  63), V( 127), V(51), V(24) } } };
 
   // Max bonus for king safety. Corresponds to start position with all the pawns
   // in front of the king and no enemy pawn on the horizon.
@@ -247,13 +246,15 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   const Color Them = (Us == WHITE ? BLACK : WHITE);
 
+  enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
+
   Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
   Bitboard ourPawns = b & pos.pieces(Us);
   Bitboard theirPawns = b & pos.pieces(Them);
   Value safety = MaxSafetyBonus;
-  File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+  File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
 
-  for (File f = kf - File(1); f <= kf + File(1); ++f)
+  for (File f = center - File(1); f <= center + File(1); ++f)
   {
       b = ourPawns & file_bb(f);
       Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
@@ -262,12 +263,11 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
       Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
 
       safety -=  ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
-               + StormDanger[std::min(f, FILE_H - f)]
-                            [file_of(ksq) == f && relative_rank(Us, ksq) == rkThem - 1 ? 3 :
-                             rkUs   == RANK_1                                          ? 0 :
-                             rkThem != rkUs + 1                                        ? 1 : 
-                             /* pawn blocked by pawn */                                  2 ]
-                            [rkThem];
+               + StormDanger
+                 [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing  :
+                  rkUs   == RANK_1                                          ? NoFriendlyPawn :
+                  rkThem == rkUs + 1                                        ? BlockedByPawn  : Unblocked]
+                 [std::min(f, FILE_H - f)][rkThem];
   }
 
   return safety;