search_qsonly.cpp

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/*---------------------------------------------------------------------+
 * File: search_qsonly.cpp
 * Project: part of belofte - A Promising Chess Program
 * Author: yves
 * SPDX-License-Identifier: GPL-2.0-only
+----------------------------------------------------------------------*/
 
#include "belofte.h"
 
//-----------------------------------------------------------------------
 
SearchEvalPosOnly::SearchEvalPosOnly()
  : bSearchAlgorithm("StaticEval")
{
}
 
SearchEvalPosOnly::~SearchEvalPosOnly()
{
}
 
bBestMoveInfo SearchEvalPosOnly::CalcBestMove(bBoard& b)
{
  bBestMoveInfo result;
  m_maxDepth = 1;
 
  movenum_t n_moves = b.generateMoves();
  bMoveList& ml = b.getMoves();
  bScore sc = RetrieveBoardEvaluation(b);
  sendInfoSearching(b, 0, "PV InitialPosScore", sc);
 
  for (movenum_t moveid = 1; moveid <= n_moves; moveid++) {
    handleInfoCurrMove(b, ml, 1, moveid);
    bBoard chldbrd(b, ml[moveid], ml.getMoveT(moveid));
    ++m_nonleafnodes;
    bScore chldscore = -Quiescence(chldbrd, -sc, 2);
    ml.updateScoreOfBestMove(moveid, chldscore);
    sendInfoSearching(b, 0, "PV MoveValue", chldscore);
  }
 
  return result;
}
 
//-----------------------------------------------------------------------
 
bScore SearchEvalPosOnly::Quiescence(bBoard& b, bScore nValueAtNullMove,
        depth_t const nDepth)
{
  if (nDepth > m_maxDepth) m_maxDepth = nDepth;
  b.generateAtLeastOneMove();
  bScore boardscore = RetrieveBoardEvaluation(b);
 
  std::string izing = std::string(b.minimizing() > 0 ? "White" : "Black") + " to move";
 
  if (belofte::realScore(boardscore) > belofte::realScore(nValueAtNullMove)) {
    return sendInfoSearching(b, nDepth, izing + " st sc better than nullmove ("
            + belofte::to_string(nValueAtNullMove)
            + ") -- early cut off", boardscore);
  }
 
  if (!b.generateAtLeastOneQSMove()) {
    // TODO: can be no moves position because of mate
    return sendInfoSearching(b, nDepth, "dead position (static eval)",
            boardscore);
  }
 
  sendInfoSearching(b, nDepth, izing + " (static eval)", boardscore);
 
  bSearchScore bestscore(boardscore, tScoreType::SC_BEST);
 
  movenum_t n_moves = b.generateMoves();
  bMoveList& ml = b.getMoves();
  for (movenum_t moveid = 1; moveid <= n_moves; moveid++) {
    if (ml[moveid].isNonSilent() || ml[moveid].isCheck()) {
      handleInfoCurrMove(b, ml, nDepth, moveid);
      bBoard chldbrd(b, ml[moveid], ml.getMoveT(moveid));
      ++m_nonleafnodes;
      bScore chldscore = -Quiescence(chldbrd, -nValueAtNullMove, nDepth + 1);
      ml.updateScoreOfBestMove(moveid, chldscore);
      if (chldscore > bestscore) {
        b.setVariation(chldbrd);
        bestscore = chldscore;
        // TODO: first capture will always be better
        if (chldscore > belofte::realScore(nValueAtNullMove)) {
          return sendInfoSearching(b, nDepth, "better than nullmove ("
                  + belofte::to_string(nValueAtNullMove)
                  + ") -- cut-off", chldscore);
        }
      }
    }
  }
 
  return sendInfoSearching(b, nDepth, "(return best)", bestscore);
}
 
//-----------------------------------------------------------------------
 
// eof