Space inflate bitbase.cpp

Also heavy cleanup while there.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/bitbase.cpp

@@ -26,7 +26,6 @@
 
 #include "bitbase.h"
 #include "bitboard.h"
-#include "move.h"
 #include "square.h"
 
 
@@ -46,30 +45,22 @@ namespace {
 
   struct KPKPosition {
     void from_index(int index);
-    int to_index() const;
     bool is_legal() const;
     bool is_immediate_draw() const;
     bool is_immediate_win() const;
-    Bitboard wk_attacks() const;
+    Bitboard wk_attacks()   const { return StepAttackBB[WK][whiteKingSquare]; }
-    Bitboard bk_attacks() const;
+    Bitboard bk_attacks()   const { return StepAttackBB[BK][blackKingSquare]; }
-    Bitboard pawn_attacks() const;
+    Bitboard pawn_attacks() const { return StepAttackBB[WP][pawnSquare]; }
 
     Square whiteKingSquare, blackKingSquare, pawnSquare;
     Color sideToMove;
   };
 
+  const int IndexMax = 2 * 24 * 64 * 64;
 
-  Result *Bitbase;
+  Result classify_wtm(const KPKPosition& pos, const Result bb[]);
-  const int IndexMax = 2*24*64*64;
+  Result classify_btm(const KPKPosition& pos, const Result bb[]);
-  int UnknownCount = 0;
-
-  void initialize();
-  bool next_iteration();
-  Result classify_wtm(const KPKPosition &p);
-  Result classify_btm(const KPKPosition &p);
   int compute_index(Square wksq, Square bksq, Square psq, Color stm);
-  int compress_result(Result r);
-
 }
 
 
@@ -78,175 +69,157 @@ namespace {
 ////
 
 void generate_kpk_bitbase(uint8_t bitbase[]) {
-  // Allocate array and initialize:
-  Bitbase = new Result[IndexMax];
-  initialize();
 
-  // Iterate until all positions are classified:
+  bool repeat;
-  while(next_iteration());
-
-  // Compress bitbase into the supplied parameter:
   int i, j, b;
-  for(i = 0; i < 24576; i++) {
+  KPKPosition pos;
-    for(b = 0, j = 0; j < 8; b |= (compress_result(Bitbase[8*i+j]) << j), j++);
+  Result bb[IndexMax];
-    assert(b == int(uint8_t(b)));
+
-    bitbase[i] = (uint8_t)b;
+  // Initialize table
+  for (i = 0; i < IndexMax; i++)
+  {
+      pos.from_index(i);
+      bb[i] = !pos.is_legal()          ? RESULT_INVALID
+             : pos.is_immediate_draw() ? RESULT_DRAW
+             : pos.is_immediate_win()  ? RESULT_WIN : RESULT_UNKNOWN;
   }
 
-  // Release allocated memory:
+  // Iterate until all positions are classified (30 cycles needed)
-  delete [] Bitbase;
+  do {
+      repeat = false;
+
+      for (i = 0; i < IndexMax; i++)
+          if (bb[i] == RESULT_UNKNOWN)
+          {
+              pos.from_index(i);
+
+              bb[i] = (pos.sideToMove == WHITE) ? classify_wtm(pos, bb)
+                                                : classify_btm(pos, bb);
+              if (bb[i] != RESULT_UNKNOWN)
+                  repeat = true;
+          }
+
+  } while (repeat);
+
+  // Compress result and map into supplied bitbase parameter
+  for (i = 0; i < 24576; i++)
+  {
+      b = 0;
+      for (j = 0; j < 8; j++)
+          if (bb[8*i+j] == RESULT_WIN || bb[8*i+j] == RESULT_LOSS)
+              b |= (1 << j);
+
+      bitbase[i] = (uint8_t)b;
+  }
 }
 
 
 namespace {
 
+  int compute_index(Square wksq, Square bksq, Square psq, Color stm) {
+
+      int p = int(square_file(psq)) + (int(square_rank(psq)) - 1) * 4;
+      int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
+
+      assert(r >= 0 && r < IndexMax);
+
+      return r;
+  }
+
   void KPKPosition::from_index(int index) {
-    int s;
+
+    int s = (index / 8192) % 24;
+
     sideToMove = Color(index % 2);
     blackKingSquare = Square((index / 2) % 64);
     whiteKingSquare = Square((index / 128) % 64);
-    s = (index / 8192) % 24;
     pawnSquare = make_square(File(s % 4), Rank(s / 4 + 1));
   }
 
-
-  int KPKPosition::to_index() const {
-    return compute_index(whiteKingSquare, blackKingSquare, pawnSquare,
-                         sideToMove);
-  }
-
-
   bool KPKPosition::is_legal() const {
-    if(whiteKingSquare == pawnSquare || whiteKingSquare == blackKingSquare ||
+
-       pawnSquare == blackKingSquare)
+    if (   whiteKingSquare == pawnSquare
+        || whiteKingSquare == blackKingSquare
+        || pawnSquare == blackKingSquare)
         return false;
-    if(sideToMove == WHITE) {
+
-      if(bit_is_set(this->wk_attacks(), blackKingSquare))
+    if (sideToMove == WHITE)
-        return false;
+    {
-      if(bit_is_set(this->pawn_attacks(), blackKingSquare))
+        if (   bit_is_set(wk_attacks(), blackKingSquare)
+            || bit_is_set(pawn_attacks(), blackKingSquare))
             return false;
     }
-    else {
+    else if (bit_is_set(bk_attacks(), whiteKingSquare))
-      if(bit_is_set(this->bk_attacks(), whiteKingSquare))
         return false;
-    }
+
     return true;
   }
 
-
   bool KPKPosition::is_immediate_draw() const {
-    if(sideToMove == BLACK) {
+
-      Bitboard wka = this->wk_attacks();
+    if (sideToMove == BLACK)
-      Bitboard bka = this->bk_attacks();
+    {
+        Bitboard wka = wk_attacks();
+        Bitboard bka = bk_attacks();
 
         // Case 1: Stalemate
-      if((bka & ~(wka | this->pawn_attacks())) == EmptyBoardBB)
+        if ((bka & ~(wka | pawn_attacks())) == EmptyBoardBB)
             return true;
 
         // Case 2: King can capture pawn
-      if(bit_is_set(bka, pawnSquare) && !bit_is_set(wka, pawnSquare))
+        if (bit_is_set(bka, pawnSquare) && !bit_is_set(wka, pawnSquare))
             return true;
     }
-    else {
+    else
+    {
         // Case 1: Stalemate
-      if(whiteKingSquare == SQ_A8 && pawnSquare == SQ_A7 &&
+        if (   whiteKingSquare == SQ_A8
-         (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
+            && pawnSquare == SQ_A7
+            && (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
             return true;
     }
-
     return false;
   }
 
-
   bool KPKPosition::is_immediate_win() const {
-    // The position is an immediate win if it is white to move and the white
+
-    // pawn can be promoted without getting captured:
+    // The position is an immediate win if it is white to move and the
-    return
+    // white pawn can be promoted without getting captured.
-      sideToMove == WHITE &&
+    return   sideToMove == WHITE
-      square_rank(pawnSquare) == RANK_7 &&
+          && square_rank(pawnSquare) == RANK_7
-      (square_distance(blackKingSquare, pawnSquare+DELTA_N) > 1 ||
+          && (   square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
-       bit_is_set(this->wk_attacks(), pawnSquare+DELTA_N));
+              || bit_is_set(wk_attacks(), pawnSquare + DELTA_N));
   }
 
-
+  Result classify_wtm(const KPKPosition& pos, const Result bb[]) {
-  Bitboard KPKPosition::wk_attacks() const {
-    return StepAttackBB[WK][whiteKingSquare];
-  }
-
-
-  Bitboard KPKPosition::bk_attacks() const {
-    return StepAttackBB[BK][blackKingSquare];
-  }
-
-
-  Bitboard KPKPosition::pawn_attacks() const {
-    return StepAttackBB[WP][pawnSquare];
-  }
-
-
-  void initialize() {
-    KPKPosition p;
-    for(int i = 0; i < IndexMax; i++) {
-      p.from_index(i);
-      if(!p.is_legal())
-        Bitbase[i] = RESULT_INVALID;
-      else if(p.is_immediate_draw())
-        Bitbase[i] = RESULT_DRAW;
-      else if(p.is_immediate_win())
-        Bitbase[i] = RESULT_WIN;
-      else {
-        Bitbase[i] = RESULT_UNKNOWN;
-        UnknownCount++;
-      }
-    }
-  }
-
-
-  bool next_iteration() {
-    KPKPosition p;
-    int previousUnknownCount = UnknownCount;
-
-    for(int i = 0; i < IndexMax; i++)
-      if(Bitbase[i] == RESULT_UNKNOWN) {
-        p.from_index(i);
-
-        Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p);
-
-        if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS ||
-           Bitbase[i] == RESULT_DRAW)
-          UnknownCount--;
-      }
-
-    return UnknownCount != previousUnknownCount;
-  }
-
-
-  Result classify_wtm(const KPKPosition &p) {
 
     // If one move leads to a position classified as RESULT_LOSS, the result
     // of the current position is RESULT_WIN. If all moves lead to positions
-    // classified as RESULT_DRAW, the current position is classified as
+    // classified as RESULT_DRAW, the current position is classified RESULT_DRAW
-    // RESULT_DRAW.  Otherwise, the current position is classified as
+    // otherwise the current position is classified as RESULT_UNKNOWN.
-    // RESULT_UNKNOWN.
 
     bool unknownFound = false;
     Bitboard b;
     Square s;
+    int idx;
 
     // King moves
-    b = p.wk_attacks();
+    b = pos.wk_attacks();
-    while(b) {
+    while (b)
+    {
         s = pop_1st_bit(&b);
-      switch(Bitbase[compute_index(s, p.blackKingSquare, p.pawnSquare,
+        idx = compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK);
-                                   BLACK)]) {
+
+        switch (bb[idx]) {
+
         case RESULT_LOSS:
             return RESULT_WIN;
 
         case RESULT_UNKNOWN:
             unknownFound = true;
-        break;
 
-      case RESULT_DRAW: case RESULT_INVALID:
+        case RESULT_DRAW:
+        case RESULT_INVALID:
              break;
 
          default:
@@ -255,37 +228,45 @@ namespace {
     }
 
     // Pawn moves
-    if(square_rank(p.pawnSquare) < RANK_7) {
+    if (square_rank(pos.pawnSquare) < RANK_7)
-      s = p.pawnSquare + DELTA_N;
+    {
-      switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s,
+        s = pos.pawnSquare + DELTA_N;
-                                   BLACK)]) {
+        idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
+
+        switch (bb[idx]) {
+
         case RESULT_LOSS:
             return RESULT_WIN;
 
         case RESULT_UNKNOWN:
             unknownFound = true;
-        break;
 
-      case RESULT_DRAW: case RESULT_INVALID:
+        case RESULT_DRAW:
+        case RESULT_INVALID:
             break;
 
         default:
             assert(false);
         }
 
-      if(square_rank(s) == RANK_3 &&
+        // Double pawn push
-         s != p.whiteKingSquare && s != p.blackKingSquare) {
+        if (   square_rank(s) == RANK_3
+            && s != pos.whiteKingSquare
+            && s != pos.blackKingSquare)
+        {
             s += DELTA_N;
-        switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s,
+            idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
-                                     BLACK)]) {
+
+            switch (bb[idx]) {
+
             case RESULT_LOSS:
                 return RESULT_WIN;
 
             case RESULT_UNKNOWN:
                 unknownFound = true;
-          break;
 
-        case RESULT_DRAW: case RESULT_INVALID:
+            case RESULT_DRAW:
+            case RESULT_INVALID:
                 break;
 
             default:
@@ -293,12 +274,11 @@ namespace {
             }
         }
     }
-
+    return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
-    return unknownFound? RESULT_UNKNOWN : RESULT_DRAW;
   }
 
 
-  Result classify_btm(const KPKPosition &p) {
+  Result classify_btm(const KPKPosition& pos, const Result bb[]) {
 
     // If one move leads to a position classified as RESULT_DRAW, the result
     // of the current position is RESULT_DRAW. If all moves lead to positions
@@ -309,42 +289,32 @@ namespace {
     bool unknownFound = false;
     Bitboard b;
     Square s;
+    int idx;
 
     // King moves
-    b = p.bk_attacks();
+    b = pos.bk_attacks();
-    while(b) {
+    while (b)
+    {
         s = pop_1st_bit(&b);
-      switch(Bitbase[compute_index(p.whiteKingSquare, s, p.pawnSquare,
+        idx = compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE);
-                                   WHITE)]) {
+
+        switch (bb[idx]) {
+
         case RESULT_DRAW:
             return RESULT_DRAW;
 
         case RESULT_UNKNOWN:
             unknownFound = true;
-        break;
 
-      case RESULT_WIN: case RESULT_INVALID:
+        case RESULT_WIN:
+        case RESULT_INVALID:
             break;
 
         default:
             assert(false);
         }
     }
-
+    return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS;
-    return unknownFound? RESULT_UNKNOWN : RESULT_LOSS;
-  }
-
-
-  int compute_index(Square wksq, Square bksq, Square psq, Color stm) {
-    int p = int(square_file(psq)) + (int(square_rank(psq)) - 1) * 4;
-    int result = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*p;
-    assert(result >= 0 && result < IndexMax);
-    return result;
-  }
-
-
-  int compress_result(Result r) {
-    return (r == RESULT_WIN || r == RESULT_LOSS)? 1 : 0;
   }
 
 }