Simplify popcnt

mstembera · zamar · commit 8fb45caadef6 · 2016-04-08T18:52:15.000+01:00
Also a speedup(about 1%) on 64-bit w/o hardware popcnt Retire Max15 and Full template parameters (Contributed by Marco Costalba) Now that we have just SW and HW versions, use template default parameter to get rid of explicit template parameters. Retire bitcount.h and move the only defined function to bitboard.h No functional change Resolves #620
diff --git a/src/bitboard.cpp b/src/bitboard.cpp
@@ -21,9 +21,9 @@
 #include <algorithm>
 
 #include "bitboard.h"
-#include "bitcount.h"
 #include "misc.h"
 
+uint8_t PopCnt16[1 << 16];
 int SquareDistance[SQUARE_NB][SQUARE_NB];
 
 Bitboard  RookMasks  [SQUARE_NB];
@@ -74,6 +74,16 @@ namespace {
     return Is64Bit ? (b * DeBruijn64) >> 58
                    : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn32) >> 26;
   }
+
+
+  // popcount16() counts the non-zero bits using SWAR-Popcount algorithm
+
+  uint8_t popcount16(uint16_t u) {
+    u -= (u >> 1) & 0x5555U;
+    u = ((u >> 2) & 0x3333U) + (u & 0x3333U);
+    u = ((u >> 4) + u) & 0x0F0FU;
+    return (u * 0x0101U) >> 8;
+  }
 }
 
 #ifdef NO_BSF
@@ -141,6 +151,9 @@ const std::string Bitboards::pretty(Bitboard b) {
 
 void Bitboards::init() {
 
+  for (unsigned i = 0; i < (1 << 16); ++i)
+      PopCnt16[i] = popcount16(i);
+
   for (Square s = SQ_A1; s <= SQ_H8; ++s)
   {
       SquareBB[s] = 1ULL << s;
@@ -265,7 +278,7 @@ namespace {
         // the number of 1s of the mask. Hence we deduce the size of the shift to
         // apply to the 64 or 32 bits word to get the index.
         masks[s]  = sliding_attack(deltas, s, 0) & ~edges;
-        shifts[s] = (Is64Bit ? 64 : 32) - popcount<Max15>(masks[s]);
+        shifts[s] = (Is64Bit ? 64 : 32) - popcount(masks[s]);
 
         // Use Carry-Rippler trick to enumerate all subsets of masks[s] and
         // store the corresponding sliding attack bitboard in reference[].
@@ -296,7 +309,7 @@ namespace {
         do {
             do
                 magics[s] = rng.sparse_rand<Bitboard>();
-            while (popcount<Max15>((magics[s] * masks[s]) >> 56) < 6);
+            while (popcount((magics[s] * masks[s]) >> 56) < 6);
 
             // A good magic must map every possible occupancy to an index that
             // looks up the correct sliding attack in the attacks[s] database.
diff --git a/src/bitboard.h b/src/bitboard.h
@@ -257,6 +257,32 @@ inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occupied) {
 }
 
 
+/// popcount() counts the number of non-zero bits in a bitboard
+
+inline int popcount(Bitboard b) {
+
+#ifndef USE_POPCNT
+
+  extern uint8_t PopCnt16[1 << 16];
+  union { Bitboard bb; uint16_t u[4]; } v = { b };
+  return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
+
+#elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
+
+  return _mm_popcnt_u64(b);
+
+#elif defined(_MSC_VER)
+
+  return (int)__popcnt64(b);
+
+#else // Assumed gcc or compatible compiler
+
+  return __builtin_popcountll(b);
+
+#endif
+}
+
+
 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
 
 #if defined(__GNUC__)
diff --git a/src/bitcount.h b/src/bitcount.h
diff --git a/src/endgame.cpp b/src/endgame.cpp
@@ -22,7 +22,6 @@
 #include <cassert>
 
 #include "bitboard.h"
-#include "bitcount.h"
 #include "endgame.h"
 #include "movegen.h"
 
diff --git a/src/evaluate.cpp b/src/evaluate.cpp
@@ -24,7 +24,7 @@
 #include <iomanip>
 #include <sstream>
 
-#include "bitcount.h"
+#include "bitboard.h"
 #include "evaluate.h"
 #include "material.h"
 #include "pawns.h"
@@ -234,7 +234,7 @@ namespace {
     {
         ei.kingRing[Them] = b | shift_bb<Down>(b);
         b &= ei.attackedBy[Us][PAWN];
-        ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
+        ei.kingAttackersCount[Us] = b ? popcount(b) : 0;
         ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
     }
     else
@@ -278,15 +278,15 @@ namespace {
             ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
             bb = b & ei.attackedBy[Them][KING];
             if (bb)
-                ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
+                ei.kingAdjacentZoneAttacksCount[Us] += popcount(bb);
         }
 
         if (Pt == QUEEN)
             b &= ~(  ei.attackedBy[Them][KNIGHT]
                    | ei.attackedBy[Them][BISHOP]
                    | ei.attackedBy[Them][ROOK]);
 
-        int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
+        int mob = popcount(b & mobilityArea[Us]);
 
         mobility[Us] += MobilityBonus[Pt][mob];
 
@@ -334,7 +334,7 @@ namespace {
             {
                 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
                 if (alignedPawns)
-                    score += RookOnPawn * popcount<Max15>(alignedPawns);
+                    score += RookOnPawn * popcount(alignedPawns);
             }
 
             // Bonus when on an open or semi-open file
@@ -399,7 +399,7 @@ namespace {
         // the pawn shelter (current 'score' value).
         attackUnits =  std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
                      +  9 * ei.kingAdjacentZoneAttacksCount[Them]
-                     + 27 * popcount<Max15>(undefended)
+                     + 27 * popcount(undefended)
                      + 11 * !!ei.pinnedPieces[Us]
                      - 64 * !pos.count<QUEEN>(Them)
                      - mg_value(score) / 8;
@@ -415,7 +415,7 @@ namespace {
                 | ei.attackedBy[Them][KING];
 
             if (b)
-                attackUnits += QueenContactCheck * popcount<Max15>(b);
+                attackUnits += QueenContactCheck * popcount(b);
         }
 
         // Analyse the enemy's safe distance checks for sliders and knights
@@ -513,7 +513,7 @@ namespace {
 
         b = weak & ~ei.attackedBy[Them][ALL_PIECES];
         if (b)
-            score += Hanging * popcount<Max15>(b);
+            score += Hanging * popcount(b);
 
         b = weak & ei.attackedBy[Us][KING];
         if (b)
@@ -533,7 +533,7 @@ namespace {
        & ~ei.attackedBy[Us][PAWN];
 
     if (b)
-        score += ThreatByPawnPush * popcount<Max15>(b);
+        score += ThreatByPawnPush * popcount(b);
 
     if (DoTrace)
         Trace::add(THREAT, Us, score);
@@ -656,7 +656,7 @@ namespace {
     assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
 
     // ...count safe + (behind & safe) with a single popcount
-    int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
+    int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
     int weight =  pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
                 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
 
diff --git a/src/pawns.cpp b/src/pawns.cpp
@@ -22,7 +22,6 @@
 #include <cassert>
 
 #include "bitboard.h"
-#include "bitcount.h"
 #include "pawns.h"
 #include "position.h"
 #include "thread.h"
@@ -114,7 +113,7 @@ namespace {
     e->kingSquares[Us] = SQ_NONE;
     e->semiopenFiles[Us] = 0xFF;
     e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
-    e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(ourPawns & DarkSquares);
+    e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
     e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
 
     // Loop through all pawns of the current color and score each pawn
@@ -233,7 +232,7 @@ Entry* probe(const Position& pos) {
 
   e->key = key;
   e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
-  e->asymmetry = popcount<Max15>(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+  e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
   return e;
 }
 
diff --git a/src/position.cpp b/src/position.cpp
@@ -24,7 +24,7 @@
 #include <iomanip>
 #include <sstream>
 
-#include "bitcount.h"
+#include "bitboard.h"
 #include "misc.h"
 #include "movegen.h"
 #include "position.h"
@@ -1170,7 +1170,7 @@ bool Position::pos_is_ok(int* failedStep) const {
           for (Color c = WHITE; c <= BLACK; ++c)
               for (PieceType pt = PAWN; pt <= KING; ++pt)
               {
-                  if (pieceCount[c][pt] != popcount<Full>(pieces(c, pt)))
+                  if (pieceCount[c][pt] != popcount(pieces(c, pt)))
                       return false;
 
                   for (int i = 0; i < pieceCount[c][pt];  ++i)
diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp
@@ -15,7 +15,6 @@
 #include "../movegen.h"
 #include "../bitboard.h"
 #include "../search.h"
-#include "../bitcount.h"
 
 #include "tbprobe.h"
 #include "tbcore.h"
@@ -39,12 +38,12 @@ static void prt_str(Position& pos, char *str, int mirror)
 
   color = !mirror ? WHITE : BLACK;
   for (pt = KING; pt >= PAWN; --pt)
-    for (i = popcount<Max15>(pos.pieces(color, pt)); i > 0; i--)
+    for (i = popcount(pos.pieces(color, pt)); i > 0; i--)
       *str++ = pchr[6 - pt];
   *str++ = 'v';
   color = ~color;
   for (pt = KING; pt >= PAWN; --pt)
-    for (i = popcount<Max15>(pos.pieces(color, pt)); i > 0; i--)
+    for (i = popcount(pos.pieces(color, pt)); i > 0; i--)
       *str++ = pchr[6 - pt];
   *str++ = 0;
 }
@@ -60,11 +59,11 @@ static uint64 calc_key(Position& pos, int mirror)
 
   color = !mirror ? WHITE : BLACK;
   for (pt = PAWN; pt <= KING; ++pt)
-    for (i = popcount<Max15>(pos.pieces(color, pt)); i > 0; i--)
+    for (i = popcount(pos.pieces(color, pt)); i > 0; i--)
       key ^= Zobrist::psq[WHITE][pt][i - 1];
   color = ~color;
   for (pt = PAWN; pt <= KING; ++pt)
-    for (i = popcount<Max15>(pos.pieces(color, pt)); i > 0; i--)
+    for (i = popcount(pos.pieces(color, pt)); i > 0; i--)
       key ^= Zobrist::psq[BLACK][pt][i - 1];
 
   return key;
