X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=aa6f7c19bc9ac9aa45b5368133d7010f155f32ee;hp=3897f4c10048bf7c164d67c4c2e9858e597c3994;hb=877b468e3e8a3b7f7482266007237c6974f7f282;hpb=436fa5c8fa5302f69a83ad28491702c5dc3d4af7

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 3897f4c1..aa6f7c19 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2009 Marco Costalba
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, 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
@@ -23,11 +23,9 @@
 //// Includes
 ////
 
-#include <algorithm>
 #include <cassert>
 
 #include "history.h"
-#include "evaluate.h"
 #include "movegen.h"
 #include "movepick.h"
 #include "search.h"
@@ -40,14 +38,23 @@
 
 namespace {
 
-  /// Variables
-
-  MovePicker::MovegenPhase PhaseTable[32];
-  int MainSearchPhaseIndex;
-  int EvasionsPhaseIndex;
-  int QsearchWithChecksPhaseIndex;
-  int QsearchWithoutChecksPhaseIndex;
-
+  enum MovegenPhase {
+    PH_TT_MOVES,       // Transposition table move and mate killer
+    PH_GOOD_CAPTURES,  // Queen promotions and captures with SEE values >= 0
+    PH_KILLERS,        // Killer moves from the current ply
+    PH_NONCAPTURES,    // Non-captures and underpromotions
+    PH_BAD_CAPTURES,   // Queen promotions and captures with SEE values < 0
+    PH_EVASIONS,       // Check evasions
+    PH_QCAPTURES,      // Captures in quiescence search
+    PH_QCHECKS,        // Non-capture checks in quiescence search
+    PH_STOP
+  };
+
+  CACHE_LINE_ALIGNMENT
+  const uint8_t MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
+  const uint8_t EvasionsPhaseTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP};
+  const uint8_t QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
+  const uint8_t QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
 }
 
 
@@ -56,195 +63,153 @@ namespace {
 ////
 
 
-/// Constructor for the MovePicker class.  Apart from the position for which
+/// Constructor for the MovePicker class. Apart from the position for which
 /// it is asked to pick legal moves, MovePicker also wants some information
 /// to help it to return the presumably good moves first, to decide which
 /// moves to return (in the quiescence search, for instance, we only want to
 /// search captures, promotions and some checks) and about how important good
 /// move ordering is at the current node.
 
-MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
-                       const SearchStack& ss, Depth d) : pos(p) {
-  pvNode = pv;
-  ttMove = ttm;
-  mateKiller = (ss.mateKiller == ttm)? MOVE_NONE : ss.mateKiller;
-  killer1 = ss.killers[0];
-  killer2 = ss.killers[1];
-  depth = d;
-  movesPicked = 0;
-  numOfMoves = 0;
-  numOfBadCaptures = 0;
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+                       SearchStack* ss, Value beta) : pos(p), H(h) {
+  int searchTT = ttm;
+  ttMoves[0].move = ttm;
+  badCaptureThreshold = 0;
+  badCaptures = moves + MOVES_MAX;
+
+  pinned = p.pinned_pieces(pos.side_to_move());
+
+  if (ss && !p.is_check())
+  {
+      ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller;
+      searchTT |= ttMoves[1].move;
+      killers[0].move = ss->killers[0];
+      killers[1].move = ss->killers[1];
+  } else
+      ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
 
   if (p.is_check())
-      phaseIndex = EvasionsPhaseIndex;
-  else if (depth > Depth(0))
-      phaseIndex = MainSearchPhaseIndex;
-  else if (depth == Depth(0))
-      phaseIndex = QsearchWithChecksPhaseIndex;
-  else
-      phaseIndex = QsearchWithoutChecksPhaseIndex;
+      phasePtr = EvasionsPhaseTable;
+  else if (d > DEPTH_ZERO)
+  {
+      // Consider sligtly negative captures as good if at low
+      // depth and far from beta.
+      if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
+          badCaptureThreshold = -PawnValueMidgame;
 
-  Color us = pos.side_to_move();
+      phasePtr = MainSearchPhaseTable;
+  }
+  else if (d >= DEPTH_QS_CHECKS)
+      phasePtr = QsearchWithChecksPhaseTable;
+  else
+  {
+      phasePtr = QsearchWithoutChecksPhaseTable;
 
-  dc = p.discovered_check_candidates(us);
-  pinned = p.pinned_pieces(us);
+      // Skip TT move if is not a capture or a promotion, this avoids
+      // qsearch tree explosion due to a possible perpetual check or
+      // similar rare cases when TT table is full.
+      if (ttm != MOVE_NONE && !pos.move_is_capture_or_promotion(ttm))
+          searchTT = ttMoves[0].move = MOVE_NONE;
+  }
 
-  finished = false;
+  phasePtr += int(!searchTT) - 1;
+  go_next_phase();
 }
 
 
-/// MovePicker::get_next_move() is the most important method of the MovePicker
-/// class.  It returns a new legal move every time it is called, until there
-/// are no more moves left of the types we are interested in.
+/// MovePicker::go_next_phase() generates, scores and sorts the next bunch
+/// of moves when there are no more moves to try for the current phase.
 
-Move MovePicker::get_next_move() {
+void MovePicker::go_next_phase() {
 
-  Move move;
+  curMove = moves;
+  phase = *(++phasePtr);
+  switch (phase) {
 
-  while (true)
-  {
-    // If we already have a list of generated moves, pick the best move from
-    // the list, and return it.
-    move = pick_move_from_list();
-    if (move != MOVE_NONE)
-    {
-        assert(move_is_ok(move));
-        return move;
-    }
-
-    // Next phase
-    phaseIndex++;
-    switch (PhaseTable[phaseIndex]) {
-
-    case PH_TT_MOVE:
-        if (ttMove != MOVE_NONE)
-        {
-            assert(move_is_ok(ttMove));
-            if (move_is_legal(pos, ttMove, pinned))
-                return ttMove;
-        }
-        break;
-
-    case PH_MATE_KILLER:
-        if (mateKiller != MOVE_NONE)
-        {
-            assert(move_is_ok(mateKiller));
-            if (move_is_legal(pos, mateKiller, pinned))
-                return mateKiller;
-        }
-        break;
-
-    case PH_GOOD_CAPTURES:
-        numOfMoves = generate_captures(pos, moves);
-        score_captures();
-        std::sort(moves, moves + numOfMoves);
-        movesPicked = 0;
-        break;
-
-    case PH_BAD_CAPTURES:
-        // It's probably a good idea to use SEE move ordering here. FIXME
-        movesPicked = 0;
-        break;
-
-    case PH_NONCAPTURES:
-        numOfMoves = generate_noncaptures(pos, moves);
-        score_noncaptures();
-        std::sort(moves, moves + numOfMoves);
-        movesPicked = 0;
-        break;
-
-    case PH_EVASIONS:
-        assert(pos.is_check());
-        numOfMoves = generate_evasions(pos, moves, pinned);
-        score_evasions();
-        std::sort(moves, moves + numOfMoves);
-        movesPicked = 0;
-        break;
-
-    case PH_QCAPTURES:
-        numOfMoves = generate_captures(pos, moves);
-        score_qcaptures();
-        std::sort(moves, moves + numOfMoves);
-        movesPicked = 0;
-        break;
-
-    case PH_QCHECKS:
-        // Perhaps we should order moves move here?  FIXME
-        numOfMoves = generate_non_capture_checks(pos, moves, dc);
-        movesPicked = 0;
-        break;
-
-    case PH_STOP:
-        return MOVE_NONE;
-
-    default:
-        assert(false);
-        return MOVE_NONE;
-    }
-  }
-}
+  case PH_TT_MOVES:
+      curMove = ttMoves;
+      lastMove = curMove + 2;
+      return;
 
+  case PH_GOOD_CAPTURES:
+      lastMove = generate<MV_CAPTURE>(pos, moves);
+      score_captures();
+      return;
+
+  case PH_KILLERS:
+      curMove = killers;
+      lastMove = curMove + 2;
+      return;
 
-/// A variant of get_next_move() which takes a lock as a parameter, used to
-/// prevent multiple threads from picking the same move at a split point.
+  case PH_NONCAPTURES:
+      lastMove = generate<MV_NON_CAPTURE>(pos, moves);
+      score_noncaptures();
+      sort_moves(moves, lastMove, &lastGoodNonCapture);
+      return;
+
+  case PH_BAD_CAPTURES:
+      // Bad captures SEE value is already calculated so just pick
+      // them in order to get SEE move ordering.
+      curMove = badCaptures;
+      lastMove = moves + MOVES_MAX;
+      return;
+
+  case PH_EVASIONS:
+      assert(pos.is_check());
+      lastMove = generate<MV_EVASION>(pos, moves);
+      score_evasions();
+      return;
+
+  case PH_QCAPTURES:
+      lastMove = generate<MV_CAPTURE>(pos, moves);
+      score_captures();
+      return;
 
-Move MovePicker::get_next_move(Lock &lock) {
+  case PH_QCHECKS:
+      lastMove = generate<MV_NON_CAPTURE_CHECK>(pos, moves);
+      return;
 
-   lock_grab(&lock);
-   if (finished)
-   {
-       lock_release(&lock);
-       return MOVE_NONE;
-   }
-   Move m = get_next_move();
-   if (m == MOVE_NONE)
-       finished = true;
+  case PH_STOP:
+      lastMove = curMove + 1; // Avoids another go_next_phase() call
+      return;
 
-   lock_release(&lock);
-   return m;
+  default:
+      assert(false);
+      return;
+  }
 }
 
 
-/// MovePicker::score_captures(), MovePicker::score_noncaptures(),
-/// MovePicker::score_evasions() and MovePicker::score_qcaptures() assign a
-/// numerical move ordering score to each move in a move list.  The moves
-/// with highest scores will be picked first by pick_move_from_list().
+/// MovePicker::score_captures(), MovePicker::score_noncaptures() and
+/// MovePicker::score_evasions() assign a numerical move ordering score
+/// to each move in a move list.  The moves with highest scores will be
+/// picked first by get_next_move().
 
 void MovePicker::score_captures() {
   // Winning and equal captures in the main search are ordered by MVV/LVA.
   // Suprisingly, this appears to perform slightly better than SEE based
-  // move ordering.  The reason is probably that in a position with a winning
+  // move ordering. The reason is probably that in a position with a winning
   // capture, capturing a more valuable (but sufficiently defended) piece
-  // first usually doesn't hurt.  The opponent will have to recapture, and
+  // first usually doesn't hurt. The opponent will have to recapture, and
   // the hanging piece will still be hanging (except in the unusual cases
   // where it is possible to recapture with the hanging piece). Exchanging
   // big pieces before capturing a hanging piece probably helps to reduce
   // the subtree size.
-  // While scoring captures it moves all captures with negative SEE values
-  // to the badCaptures[] array.
+  // In main search we want to push captures with negative SEE values to
+  // badCaptures[] array, but instead of doing it now we delay till when
+  // the move has been picked up in pick_move_from_list(), this way we save
+  // some SEE calls in case we get a cutoff (idea from Pablo Vazquez).
   Move m;
-  int seeValue;
 
-  for (int i = 0; i < numOfMoves; i++)
+  // Use MVV/LVA ordering
+  for (MoveStack* cur = moves; cur != lastMove; cur++)
   {
-      m = moves[i].move;
-      seeValue = pos.see(m);
-      if (seeValue >= 0)
-      {
-          if (move_promotion(m))
-              moves[i].score = QueenValueMidgame;
-          else
-              moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
-                              -int(pos.type_of_piece_on(move_from(m)));
-      }
+      m = cur->move;
+      if (move_is_promotion(m))
+          cur->score = QueenValueMidgame;
       else
-      {
-          // Losing capture, move it to the badCaptures[] array
-          assert(numOfBadCaptures < 63);
-          moves[i].score = seeValue;
-          badCaptures[numOfBadCaptures++] = moves[i];
-          moves[i--] = moves[--numOfMoves];
-      }
+          cur->score =  pos.midgame_value_of_piece_on(move_to(m))
+                      - pos.type_of_piece_on(move_from(m));
   }
 }
 
@@ -253,156 +218,140 @@ void MovePicker::score_noncaptures() {
   // piece/square tables values. This seems to be better then a
   // random choice when we don't have an history for any move.
   Move m;
-  int hs;
+  Piece piece;
+  Square from, to;
 
-  for (int i = 0; i < numOfMoves; i++)
+  for (MoveStack* cur = moves; cur != lastMove; cur++)
   {
-      m = moves[i].move;
-
-      if (m == killer1)
-          hs = HistoryMax + 2;
-      else if (m == killer2)
-          hs = HistoryMax + 1;
-      else
-          hs = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
-
-      // Ensure history is always preferred to pst
-      if (hs > 0)
-          hs += 1000;
-
-      // pst based scoring
-      moves[i].score = hs + pos.mg_pst_delta(m);
+      m = cur->move;
+      from = move_from(m);
+      to = move_to(m);
+      piece = pos.piece_on(from);
+      cur->score = H.value(piece, to) + H.gain(piece, to);
   }
 }
 
 void MovePicker::score_evasions() {
+  // Try good captures ordered by MVV/LVA, then non-captures if
+  // destination square is not under attack, ordered by history
+  // value, and at the end bad-captures and non-captures with a
+  // negative SEE. This last group is ordered by the SEE score.
+  Move m;
+  int seeScore;
 
-  for (int i = 0; i < numOfMoves; i++)
-  {
-      Move m = moves[i].move;
-      if (m == ttMove)
-          moves[i].score = 2*HistoryMax;
-      else if (!pos.square_is_empty(move_to(m)))
-      {
-          int seeScore = pos.see(m);
-          moves[i].score = (seeScore >= 0)? seeScore + HistoryMax : seeScore;
-      } else
-          moves[i].score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
-  }
-}
-
-void MovePicker::score_qcaptures() {
+  // Skip if we don't have at least two moves to order
+  if (lastMove < moves + 2)
+      return;
 
-  // Use MVV/LVA ordering
-  for (int i = 0; i < numOfMoves; i++)
+  for (MoveStack* cur = moves; cur != lastMove; cur++)
   {
-      Move m = moves[i].move;
-      if (move_promotion(m))
-          moves[i].score = QueenValueMidgame;
+      m = cur->move;
+      if ((seeScore = pos.see_sign(m)) < 0)
+          cur->score = seeScore - History::MaxValue; // Be sure we are at the bottom
+      else if (pos.move_is_capture(m))
+          cur->score =  pos.midgame_value_of_piece_on(move_to(m))
+                      - pos.type_of_piece_on(move_from(m)) + History::MaxValue;
       else
-          moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
-                          -int(pos.type_of_piece_on(move_from(m)));
+          cur->score = H.value(pos.piece_on(move_from(m)), move_to(m));
   }
 }
 
+/// MovePicker::get_next_move() is the most important method of the MovePicker
+/// class. It returns a new legal move every time it is called, until there
+/// are no more moves left.
+/// It picks the move with the biggest score from a list of generated moves taking
+/// care not to return the tt move if has already been searched previously.
+/// Note that this function is not thread safe so should be lock protected by
+/// caller when accessed through a shared MovePicker object.
 
-/// MovePicker::pick_move_from_list() picks the move with the biggest score
-/// from a list of generated moves (moves[] or badCaptures[], depending on
-/// the current move generation phase).  It takes care not to return the
-/// transposition table move if that has already been serched previously.
-
-Move MovePicker::pick_move_from_list() {
-
-  assert(movesPicked >= 0);
-  assert(!pos.is_check() || PhaseTable[phaseIndex] == PH_EVASIONS || PhaseTable[phaseIndex] == PH_STOP);
-  assert( pos.is_check() || PhaseTable[phaseIndex] != PH_EVASIONS);
-
-  switch (PhaseTable[phaseIndex]) {
-
-  case PH_GOOD_CAPTURES:
-  case PH_NONCAPTURES:
-      while (movesPicked < numOfMoves)
-      {
-          Move move = moves[movesPicked++].move;
-          if (   move != ttMove
-              && move != mateKiller
-              && pos.pl_move_is_legal(move, pinned))
-              return move;
-      }
-      break;
-
-  case PH_EVASIONS:
-      if (movesPicked < numOfMoves)
-          return moves[movesPicked++].move;
+Move MovePicker::get_next_move() {
 
-      break;
+  Move move;
 
-  case PH_BAD_CAPTURES:
-      while (movesPicked < numOfBadCaptures)
+  while (true)
+  {
+      while (curMove != lastMove)
       {
-          Move move = badCaptures[movesPicked++].move;
-          if (   move != ttMove
-              && move != mateKiller
-              && pos.pl_move_is_legal(move, pinned))
+          switch (phase) {
+
+          case PH_TT_MOVES:
+              move = (curMove++)->move;
+              if (   move != MOVE_NONE
+                  && move_is_legal(pos, move, pinned))
+                  return move;
+              break;
+
+          case PH_GOOD_CAPTURES:
+              move = pick_best(curMove++, lastMove).move;
+              if (   move != ttMoves[0].move
+                  && move != ttMoves[1].move
+                  && pos.pl_move_is_legal(move, pinned))
+              {
+                  // Check for a non negative SEE now
+                  int seeValue = pos.see_sign(move);
+                  if (seeValue >= badCaptureThreshold)
+                      return move;
+
+                  // Losing capture, move it to the tail of the array, note
+                  // that move has now been already checked for legality.
+                  (--badCaptures)->move = move;
+                  badCaptures->score = seeValue;
+              }
+              break;
+
+          case PH_KILLERS:
+              move = (curMove++)->move;
+              if (   move != MOVE_NONE
+                  && move_is_legal(pos, move, pinned)
+                  && move != ttMoves[0].move
+                  && move != ttMoves[1].move
+                  && !pos.move_is_capture(move))
+                  return move;
+              break;
+
+          case PH_NONCAPTURES:
+
+              // Sort negative scored moves only when we get there
+              if (curMove == lastGoodNonCapture)
+                  insertion_sort<MoveStack>(lastGoodNonCapture, lastMove);
+
+              move = (curMove++)->move;
+              if (   move != ttMoves[0].move
+                  && move != ttMoves[1].move
+                  && move != killers[0].move
+                  && move != killers[1].move
+                  && pos.pl_move_is_legal(move, pinned))
+                  return move;
+              break;
+
+          case PH_BAD_CAPTURES:
+              move = pick_best(curMove++, lastMove).move;
               return move;
-      }
-      break;
 
-  case PH_QCAPTURES:
-  case PH_QCHECKS:
-      while (movesPicked < numOfMoves)
-      {
-          Move move = moves[movesPicked++].move;
-          // Maybe postpone the legality check until after futility pruning?
-          if (   move != ttMove
-              && pos.pl_move_is_legal(move, pinned))
-              return move;
+          case PH_EVASIONS:
+          case PH_QCAPTURES:
+              move = pick_best(curMove++, lastMove).move;
+              if (   move != ttMoves[0].move
+                  && pos.pl_move_is_legal(move, pinned))
+                  return move;
+              break;
+
+          case PH_QCHECKS:
+              move = (curMove++)->move;
+              if (   move != ttMoves[0].move
+                  && pos.pl_move_is_legal(move, pinned))
+                  return move;
+              break;
+
+          case PH_STOP:
+              return MOVE_NONE;
+
+          default:
+              assert(false);
+              break;
+          }
       }
-      break;
-
-  default:
-      break;
+      go_next_phase();
   }
-  return MOVE_NONE;
 }
 
-
-/// MovePicker::init_phase_table() initializes the PhaseTable[],
-/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
-/// and QsearchWithoutChecksPhaseIndex. It is only called once during
-/// program startup, and never again while the program is running.
-
-void MovePicker::init_phase_table() {
-
-  int i = 0;
-
-  // Main search
-  MainSearchPhaseIndex = i - 1;
-  PhaseTable[i++] = PH_TT_MOVE;
-  PhaseTable[i++] = PH_MATE_KILLER;
-  PhaseTable[i++] = PH_GOOD_CAPTURES;
-  // PH_KILLER_1 and PH_KILLER_2 are not yet used.
-  // PhaseTable[i++] = PH_KILLER_1;
-  // PhaseTable[i++] = PH_KILLER_2;
-  PhaseTable[i++] = PH_NONCAPTURES;
-  PhaseTable[i++] = PH_BAD_CAPTURES;
-  PhaseTable[i++] = PH_STOP;
-
-  // Check evasions
-  EvasionsPhaseIndex = i - 1;
-  PhaseTable[i++] = PH_EVASIONS;
-  PhaseTable[i++] = PH_STOP;
-
-  // Quiescence search with checks
-  QsearchWithChecksPhaseIndex = i - 1;
-  PhaseTable[i++] = PH_TT_MOVE;
-  PhaseTable[i++] = PH_QCAPTURES;
-  PhaseTable[i++] = PH_QCHECKS;
-  PhaseTable[i++] = PH_STOP;
-
-  // Quiescence search without checks
-  QsearchWithoutChecksPhaseIndex = i - 1;
-  PhaseTable[i++] = PH_TT_MOVE;
-  PhaseTable[i++] = PH_QCAPTURES;
-  PhaseTable[i++] = PH_STOP;
-}