New Imbalance Tables Tweak

Imbalance tables tweaked to contain MiddleGame and Endgame values, instead of a single value.

The idea started from Fisherman, which requested my help to tune the values back in June/July,
so I tuned the values back then, and we were able to accomplish good results,
but not enough to pass both STC and LTC tests.

So after the recent changes, I decided to give it another shot, and I am glad that it was a successful attempt.

A special thanks goes also to mstembera, which notified me a simple way to let the patch perform a little better.

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 115976 W: 23124 L: 22695 D: 70157
Ptnml(0-2): 2074, 13652, 26285, 13725, 2252
https://tests.stockfishchess.org/tests/view/5fc92d2d42a050a89f02ccc8

Passed LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 156304 W: 20617 L: 20024 D: 115663
Ptnml(0-2): 1138, 14647, 46084, 15050, 1233
https://tests.stockfishchess.org/tests/view/5fc9fee142a050a89f02cd3e

closes https://github.com/official-stockfish/Stockfish/pull/3255

Bench: 4278746

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ef33adf5d774a56fb306a6333c4774fd3fd11daa..c507aa06a85f8a2bf4c84e4e038f3d0cdf72fc86 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -594,7 +594,7 @@ namespace {
     int kingFlankDefense = popcount(b3);
 
     kingDanger +=        kingAttackersCount[Them] * kingAttackersWeight[Them] // (~10 Elo)
-                 + 185 * popcount(kingRing[Us] & weak)                        // (~15 Elo)
+                 + 183 * popcount(kingRing[Us] & weak)                        // (~15 Elo)
                  + 148 * popcount(unsafeChecks)                               // (~4 Elo)
                  +  98 * popcount(pos.blockers_for_king(Us))                  // (~2 Elo)
                  +  69 * kingAttacksCount[Them]                               // (~0.5 Elo)

diff --git a/src/material.cpp b/src/material.cpp
index 870a5e112cb8ed25536ec10a7165f8031c57702f..f77972e352c0d9395054750bca0ebe93aef3e73c 100644 (file)
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -25,31 +25,34 @@
 using namespace std;
 
 namespace {
+  #define S(mg, eg) make_score(mg, eg)
 
   // Polynomial material imbalance parameters
 
-  constexpr int QuadraticOurs[][PIECE_TYPE_NB] = {
+  constexpr Score QuadraticOurs[][PIECE_TYPE_NB] = {
     //            OUR PIECES
     // pair pawn knight bishop rook queen
-    {1438                               }, // Bishop pair
-    {  40,   38                         }, // Pawn
-    {  32,  255, -62                    }, // Knight      OUR PIECES
-    {   0,  104,   4,    0              }, // Bishop
-    { -26,   -2,  47,   105,  -208      }, // Rook
-    {-189,   24, 117,   133,  -134, -6  }  // Queen
+    {S(1419, 1455)                                                                  }, // Bishop pair
+    {S( 101,   28), S( 37,  39)                                                     }, // Pawn
+    {S(  57,   64), S(249, 187), S(-49, -62)                                        }, // Knight      OUR PIECES
+    {S(   0,    0), S(118, 137), S( 10,  27), S(  0,   0)                           }, // Bishop
+    {S( -63,  -68), S( -5,   3), S(100,  81), S(132, 118), S(-246, -244)            }, // Rook
+    {S(-210, -211), S( 37,  14), S(147, 141), S(161, 105), S(-158, -174), S(-9,-31) }  // Queen
   };
 
-  constexpr int QuadraticTheirs[][PIECE_TYPE_NB] = {
+  constexpr Score QuadraticTheirs[][PIECE_TYPE_NB] = {
     //           THEIR PIECES
     // pair pawn knight bishop rook queen
-    {                                   }, // Bishop pair
-    {  36,                              }, // Pawn
-    {   9,   63,                        }, // Knight      OUR PIECES
-    {  59,   65,  42,                   }, // Bishop
-    {  46,   39,  24,   -24,            }, // Rook
-    {  97,  100, -42,   137,  268,      }  // Queen
+    {                                                                               }, // Bishop pair
+    {S(  33,  30)                                                                   }, // Pawn
+    {S(  46,  18), S(106,  84)                                                      }, // Knight      OUR PIECES
+    {S(  75,  35), S( 59,  44), S( 60,  15)                                         }, // Bishop
+    {S(  26,  35), S(  6,  22), S( 38,  39), S(-12,  -2)                            }, // Rook
+    {S(  97,  93), S(100, 163), S(-58, -91), S(112, 192), S(276, 225)               }  // Queen
   };
 
+  #undef S
+
   // Endgame evaluation and scaling functions are accessed directly and not through
   // the function maps because they correspond to more than one material hash key.
   Endgame<KXK>    EvaluateKXK[] = { Endgame<KXK>(WHITE),    Endgame<KXK>(BLACK) };
@@ -82,11 +85,11 @@ namespace {
   /// piece type for both colors.
 
   template<Color Us>
-  int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
+  Score imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
 
     constexpr Color Them = ~Us;
 
-    int bonus = 0;
+    Score bonus = SCORE_ZERO;
 
     // Second-degree polynomial material imbalance, by Tord Romstad
     for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
@@ -213,7 +216,7 @@ Entry* probe(const Position& pos) {
   { pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
     pos.count<BISHOP>(BLACK)    , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
 
-  e->value = int16_t((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
+  e->score = (imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16;
   return e;
 }
 

diff --git a/src/material.h b/src/material.h
index 80d016551113e7bcac6eb03b6c4713bad2d5aac3..28da59dbf3303ddd0ac1319acd0948669f232948 100644 (file)
--- a/src/material.h
+++ b/src/material.h
@@ -37,8 +37,8 @@ namespace Material {
 
 struct Entry {
 
-  Score imbalance() const { return make_score(value, value); }
-  Phase game_phase() const { return gamePhase; }
+  Score imbalance() const { return score; }
+  Phase game_phase() const { return (Phase)gamePhase; }
   bool specialized_eval_exists() const { return evaluationFunction != nullptr; }
   Value evaluate(const Position& pos) const { return (*evaluationFunction)(pos); }
 
@@ -57,9 +57,9 @@ struct Entry {
   const EndgameBase<Value>* evaluationFunction;
   const EndgameBase<ScaleFactor>* scalingFunction[COLOR_NB]; // Could be one for each
                                                              // side (e.g. KPKP, KBPsK)
-  int16_t value;
+  Score score;
+  int16_t gamePhase;
   uint8_t factor[COLOR_NB];
-  Phase gamePhase;
 };
 
 typedef HashTable<Entry, 8192> Table;

diff --git a/src/pawns.cpp b/src/pawns.cpp
index b6d2900305aa25e3119ff067a670f194f6a78090..16dbf27a5b105c3f8364d197b3913ac5f337ddfd 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -66,6 +66,7 @@ namespace {
     { V(-17), V( -13), V( 100), V(  4), V(  9), V(-16), V(-31) }
   };
 
+
   // KingOnFile[semi-open Us][semi-open Them] contains bonuses/penalties
   // for king when the king is on a semi-open or open file.
   constexpr Score KingOnFile[2][2] = {{ S(-19,12), S(-6, 7)  },