Document why initing eval tables

Instead of hard-code the weights in a big table,
we prefer to calculate them out of few parameters
at startup. This allows to keep low the number of
independent parameters and hence is good for tuning
and for a better insight in the meaning of the numbers.

No functional change.

diff --git a/src/pawns.cpp b/src/pawns.cpp
index d8d8243fc9570ab08b1cb7233544fabd7e8e61cf..2fc8e73666fb78e94d46b75f0dca635f80e6b280 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -194,19 +194,24 @@ namespace {
 
 namespace Pawns {
 
+/// init() initializes some tables used by evaluation. Instead of hard-coded
+/// tables, when makes sense, we prefer to calculate them with a formula to
+/// reduce independent parameters and to allow easier tuning and better insight.
+
 void init()
 {
-  const int c[RANK_NB] = {0, 6, 15, 10, 57, 75, 135, 258};
+  static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
 
-  for (Rank r = RANK_2; r <= RANK_7; ++r)
-      for (int opposed = false; opposed <= true; ++opposed)
-          for (int phalanx = false; phalanx <= true; ++phalanx)
+  for (int opposed = 0; opposed <= 1; ++opposed)
+      for (int phalanx = 0; phalanx <= 1; ++phalanx)
+          for (Rank r = RANK_2; r < RANK_8; ++r)
           {
-              int bonus = c[r] + (phalanx ? (c[r + 1] - c[r]) / 2 : 0);
+              int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
               Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
           }
 }
 
+
 /// probe() takes a position as input, computes a Entry object, and returns a
 /// pointer to it. The result is also stored in a hash table, so we don't have
 /// to recompute everything when the same pawn structure occurs again.