Retire CenterBind

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 1099c5a48a67a9e5f15f1526ce720c299800c06a..8e4fbe344e2ec576b2b434bf2021ca672062e039 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -1,7 +1,8 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)

-  Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad

 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by


@@ -24,56 +25,69 @@
 #include "bitcount.h"
 #include "pawns.h"
 #include "position.h"
 #include "bitcount.h"
 #include "pawns.h"
 #include "position.h"

+#include "thread.h"

 
 namespace {
 
   #define V Value
   #define S(mg, eg) make_score(mg, eg)
 
 
 namespace {
 
   #define V Value
   #define S(mg, eg) make_score(mg, eg)
 

+  // Isolated pawn penalty by opposed flag and file
+  const Score Isolated[2][FILE_NB] = {
+    { S(37, 45), S(54, 52), S(60, 52), S(60, 52),
+      S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
+    { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
+      S(40, 35), S(40, 35), S(36, 35), S(25, 30) } };
+
+  // Backward pawn penalty by opposed flag
+  const Score Backward[2] = { S(67, 42), S(49, 24) };
+  
+  // Unsupported pawn penalty for pawns which are neither isolated or backward,
+  // by number of pawns it supports [less than 2 / exactly 2].
+  const Score Unsupported[2] = { S(20, 10), S(25, 15) };
+
+  // Connected pawn bonus by opposed, phalanx, twice supported and rank
+  Score Connected[2][2][2][RANK_NB];
+  

   // Doubled pawn penalty by file
   const Score Doubled[FILE_NB] = {
     S(13, 43), S(20, 48), S(23, 48), S(23, 48),
     S(23, 48), S(23, 48), S(20, 48), S(13, 43) };
 
   // Doubled pawn penalty by file
   const Score Doubled[FILE_NB] = {
     S(13, 43), S(20, 48), S(23, 48), S(23, 48),
     S(23, 48), S(23, 48), S(20, 48), S(13, 43) };
 

-  // Isolated pawn penalty by opposed flag and file
-  const Score Isolated[2][FILE_NB] = {
-  { S(37, 45), S(54, 52), S(60, 52), S(60, 52),
-    S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
-  { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
-    S(40, 35), S(40, 35), S(36, 35), S(25, 30) } };
-
-  // Backward pawn penalty by opposed flag and file
-  const Score Backward[2][FILE_NB] = {
-  { S(30, 42), S(43, 46), S(49, 46), S(49, 46),
-    S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
-  { S(20, 28), S(29, 31), S(33, 31), S(33, 31),
-    S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
-
-  // Connected pawn bonus by opposed, phalanx flags and rank
-  Score Connected[2][2][RANK_NB];
-
-  // Levers bonus by rank
+  // Lever bonus by rank

   const Score Lever[RANK_NB] = {
   const Score Lever[RANK_NB] = {

-    S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
-    S(20,20), S(40,40), S(0, 0), S(0, 0) };
-
-  // Unsupported pawn penalty
-  const Score UnsupportedPawnPenalty = S(20, 10);
-
-  // Weakness of our pawn shelter in front of the king indexed by [rank]
-  const Value ShelterWeakness[RANK_NB] =
-  { V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
-
-  // Danger of enemy pawns moving toward our king indexed by
-  // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
-  const Value StormDanger[][RANK_NB] = {
-  { V( 0),  V(64), V(128), V(51), V(26) },
-  { V(26),  V(32), V( 96), V(38), V(20) },
-  { V( 0),  V( 0), V(160), V(25), V(13) } };
+    S( 0,  0), S( 0,  0), S(0, 0), S(0, 0),
+    S(20, 20), S(40, 40), S(0, 0), S(0, 0) };
+
+  // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
+  const Value ShelterWeakness[][RANK_NB] = {
+    { V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
+    { V(120), V( 0), V(28), V(76), V(88), V(103), V(104) },
+    { V(101), V( 7), V(54), V(78), V(77), V( 92), V(101) },
+    { V( 80), V(11), V(44), V(68), V(87), V( 90), V(119) } };
+
+  // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
+  const Value StormDanger[][4][RANK_NB] = {
+    { { V( 0),  V(  67), V( 134), V(38), V(32) },
+      { V( 0),  V(  57), V( 139), V(37), V(22) },
+      { V( 0),  V(  43), V( 115), V(43), V(27) },
+      { V( 0),  V(  68), V( 124), V(57), V(32) } },
+    { { V(20),  V(  43), V( 100), V(56), V(20) },
+      { V(23),  V(  20), V(  98), V(40), V(15) },
+      { V(23),  V(  39), V( 103), V(36), V(18) },
+      { V(28),  V(  19), V( 108), V(42), V(26) } },
+    { { V( 0),  V(   0), V(  75), V(14), V( 2) },
+      { V( 0),  V(   0), V( 150), V(30), V( 4) },
+      { V( 0),  V(   0), V( 160), V(22), V( 5) },
+      { V( 0),  V(   0), V( 166), V(24), V(13) } },
+    { { V( 0),  V(-283), V(-281), V(57), V(31) },
+      { V( 0),  V(  58), V( 141), V(39), V(18) },
+      { V( 0),  V(  65), V( 142), V(48), V(32) },
+      { V( 0),  V(  60), V( 126), V(51), V(19) } } };

 
   // 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.
 
   // 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.

-  const Value MaxSafetyBonus = V(263);
+  const Value MaxSafetyBonus = V(258);

 
   #undef S
   #undef V
 
   #undef S
   #undef V


@@ -86,17 +100,17 @@ namespace {
     const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
     const Square Left  = (Us == WHITE ? DELTA_NW : DELTA_SE);
 
     const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
     const Square Left  = (Us == WHITE ? DELTA_NW : DELTA_SE);
 

-    Bitboard b, p, doubled, connected;
+    Bitboard b, neighbours, doubled, supported, phalanx;

     Square s;
     Square s;

-    bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
-    Score value = SCORE_ZERO;
-    const Square* pl = pos.list<PAWN>(Us);
+    bool passed, isolated, opposed, backward, lever, connected;
+    Score score = SCORE_ZERO;
+    const Square* pl = pos.squares<PAWN>(Us);

     const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
 
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 
     const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
 
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 

-    e->passedPawns[Us] = 0;
+    e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;

     e->kingSquares[Us] = SQ_NONE;
     e->semiopenFiles[Us] = 0xFF;
     e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
     e->kingSquares[Us] = SQ_NONE;
     e->semiopenFiles[Us] = 0xFF;
     e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);


@@ -110,34 +124,31 @@ namespace {
 
         File f = file_of(s);
 
 
         File f = file_of(s);
 

-        // This file cannot be semi-open

         e->semiopenFiles[Us] &= ~(1 << f);
         e->semiopenFiles[Us] &= ~(1 << f);

+        e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);

 
 

-        // Previous rank
-        p = rank_bb(s - pawn_push(Us));
-
-        // Flag the pawn as passed, isolated, doubled,
-        // unsupported or connected (but not the backward one).
-        connected   =   ourPawns   & adjacent_files_bb(f) & (rank_bb(s) | p);
-        phalanx     =   connected  & rank_bb(s);
-        unsupported = !(ourPawns   & adjacent_files_bb(f) & p);
-        isolated    = !(ourPawns   & adjacent_files_bb(f));
+        // Flag the pawn
+        neighbours  =   ourPawns   & adjacent_files_bb(f);

         doubled     =   ourPawns   & forward_bb(Us, s);
         opposed     =   theirPawns & forward_bb(Us, s);
         passed      = !(theirPawns & passed_pawn_mask(Us, s));
         lever       =   theirPawns & pawnAttacksBB[s];
         doubled     =   ourPawns   & forward_bb(Us, s);
         opposed     =   theirPawns & forward_bb(Us, s);
         passed      = !(theirPawns & passed_pawn_mask(Us, s));
         lever       =   theirPawns & pawnAttacksBB[s];

+        phalanx     =   neighbours & rank_bb(s);
+        supported   =   neighbours & rank_bb(s - Up);
+        connected   =   supported | phalanx;
+        isolated    =  !neighbours;

 
         // Test for backward pawn.
 
         // Test for backward pawn.

-        // If the pawn is passed, isolated, or connected it cannot be
+        // If the pawn is passed, isolated, lever or connected it cannot be

         // backward. If there are friendly pawns behind on adjacent files
         // backward. If there are friendly pawns behind on adjacent files

-        // or if it can capture an enemy pawn it cannot be backward either.
-        if (   (passed | isolated | connected)
+        // or if it is sufficiently advanced, it cannot be backward either.
+        if (   (passed | isolated | lever | connected)

             || (ourPawns & pawn_attack_span(Them, s))
             || (ourPawns & pawn_attack_span(Them, s))

-            || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+            || (relative_rank(Us, s) >= RANK_5))

             backward = false;
         else
         {
             backward = false;
         else
         {

-            // We now know that there are no friendly pawns beside or behind this
+            // We now know there are no friendly pawns beside or behind this

             // pawn on adjacent files. We now check whether the pawn is
             // backward by looking in the forward direction on the adjacent
             // files, and picking the closest pawn there.
             // pawn on adjacent files. We now check whether the pawn is
             // backward by looking in the forward direction on the adjacent
             // files, and picking the closest pawn there.


@@ -152,44 +163,44 @@ namespace {
         assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
 
         // Passed pawns will be properly scored in evaluation because we need
         assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
 
         // Passed pawns will be properly scored in evaluation because we need

-        // full attack info to evaluate passed pawns. Only the frontmost passed
+        // full attack info to evaluate them. Only the frontmost passed

         // pawn on each file is considered a true passed pawn.
         if (passed && !doubled)
             e->passedPawns[Us] |= s;
 
         // Score this pawn
         if (isolated)
         // pawn on each file is considered a true passed pawn.
         if (passed && !doubled)
             e->passedPawns[Us] |= s;
 
         // Score this pawn
         if (isolated)

-            value -= Isolated[opposed][f];
+            score -= Isolated[opposed][f];

 
 

-        if (unsupported && !isolated)
-            value -= UnsupportedPawnPenalty;
+        else if (backward)
+            score -= Backward[opposed];

 
 

-        if (doubled)
-            value -= Doubled[f] / distance<Rank>(s, Square(lsb(doubled)));
-
-        if (backward)
-            value -= Backward[opposed][f];
+        else if (!supported)
+            score -= Unsupported[more_than_one(neighbours & rank_bb(s + Up))];

 
         if (connected)
 
         if (connected)

-            value += Connected[opposed][phalanx][relative_rank(Us, s)];
+            score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
+
+        if (doubled)
+            score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));

 
         if (lever)
 
         if (lever)

-            value += Lever[relative_rank(Us, s)];
+            score += Lever[relative_rank(Us, s)];

     }
 
     b = e->semiopenFiles[Us] ^ 0xFF;
     e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
 
     }
 
     b = e->semiopenFiles[Us] ^ 0xFF;
     e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
 

-    return value;
+    return score;

   }
 
 } // namespace
 
 namespace Pawns {
 
   }
 
 } // 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.
+/// Pawns::init() initializes some tables needed by evaluation. Instead of using
+/// 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()
 {
 
 void init()
 {


@@ -197,28 +208,32 @@ void init()
 
   for (int opposed = 0; opposed <= 1; ++opposed)
       for (int phalanx = 0; phalanx <= 1; ++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 = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
-              Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
-          }
+          for (int apex = 0; apex <= 1; ++apex)
+              for (Rank r = RANK_2; r < RANK_8; ++r)
+  {
+      int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+      v += (apex ? v / 2 : 0);
+      Connected[opposed][phalanx][apex][r] = make_score(3 * v / 2, v);
+  }

 }
 
 
 }
 
 

-/// 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.
+/// Pawns::probe() looks up the current position's pawns configuration in
+/// the pawns hash table. It returns a pointer to the Entry if the position
+/// is found. Otherwise a new Entry is computed and stored there, so we don't
+/// have to recompute all when the same pawns configuration occurs again.

 
 

-Entry* probe(const Position& pos, Table& entries) {
+Entry* probe(const Position& pos) {

 
   Key key = pos.pawn_key();
 
   Key key = pos.pawn_key();

-  Entry* e = entries[key];
+  Entry* e = pos.this_thread()->pawnsTable[key];

 
   if (e->key == key)
       return e;
 
   e->key = key;
 
   if (e->key == key)
       return e;
 
   e->key = key;

-  e->value = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+  e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+  e->asymmetry = popcount<Max15>(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);

   return e;
 }
 
   return e;
 }
 


@@ -230,15 +245,16 @@ template<Color Us>
 Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   const Color Them = (Us == WHITE ? BLACK : WHITE);
 Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   const Color Them = (Us == WHITE ? BLACK : WHITE);

-  const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
+
+  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;
 
   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;
   {
       b = ourPawns & file_bb(f);
       Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;


@@ -246,14 +262,12 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
       b  = theirPawns & file_bb(f);
       Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
 
       b  = theirPawns & file_bb(f);
       Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
 

-      if (   (Edges & make_square(f, rkThem))
-          && file_of(ksq) == f
-          && relative_rank(Us, ksq) == rkThem - 1)
-          safety += 200;
-      else
-          safety -=  ShelterWeakness[rkUs]
-                   + StormDanger[rkUs   == RANK_1   ? 0 :
-                                 rkThem != rkUs + 1 ? 1 : 2][rkThem];
+      safety -=  ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+               + 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;
   }
 
   return safety;


@@ -268,14 +282,14 @@ Score Entry::do_king_safety(const Position& pos, Square ksq) {
 
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.can_castle(Us);
 
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.can_castle(Us);

-  minKPdistance[Us] = 0;
+  int minKingPawnDistance = 0;

 
   Bitboard pawns = pos.pieces(Us, PAWN);
   if (pawns)
 
   Bitboard pawns = pos.pieces(Us, PAWN);
   if (pawns)

-      while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+      while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}

 
   if (relative_rank(Us, ksq) > RANK_4)
 
   if (relative_rank(Us, ksq) > RANK_4)

-      return make_score(0, -16 * minKPdistance[Us]);
+      return make_score(0, -16 * minKingPawnDistance);

 
   Value bonus = shelter_storm<Us>(pos, ksq);
 
 
   Value bonus = shelter_storm<Us>(pos, ksq);
 


@@ -286,7 +300,7 @@ Score Entry::do_king_safety(const Position& pos, Square ksq) {
   if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
       bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
 
   if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
       bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
 

-  return make_score(bonus, -16 * minKPdistance[Us]);
+  return make_score(bonus, -16 * minKingPawnDistance);

 }
 
 // Explicit template instantiation
 }
 
 // Explicit template instantiation