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"
 
//-----------------------------------------------------------------------
 
/**
 * Root search for algorithm
 * @param b board
 * @param ml movelist of this position
 */
bScore SearchEvalPosOnly::CalcBestMove(bBoard& b, bMoveList& ml)
{
  depth_t nDepth = 1;
  adjustMaxSearchedDepth(nDepth);
  CheckIfAbortingSearch();
  bScore terminalScore = RetrieveBoardEvaluation(b);
 
  movenum_t n_moves = ml.getNumberOfMoves();
  DEBUG_sendInfoSearching(b, nDepth, "PV InitialPosScore", terminalScore);
 
  depth_t nNewDepth = nDepth + 1;
  ml.clearScores();
  for (movenum_t moveid = 1; moveid <= n_moves; ++moveid) {
    bMove m(ml[moveid]);
    sendInfoCurrMove(b, nDepth, m, moveid);
    bBoard chldbrd(b, m);
    b.applyMove(m);
    ++m_nonleafnodes;
    bMoveList chldML;
    bSearchScore chldscore(-Quiescence(chldbrd, chldML, -terminalScore, nNewDepth));
    ml.setScoreOfMove(moveid, chldscore.getScore());
    DEBUG_sendInfoSearching(b, nDepth, "PV MoveValue", chldscore.getScore());
  }
 
  return SCORE_UNDEFINED;
}
 
//-----------------------------------------------------------------------
 
bScore SearchEvalPosOnly::Quiescence(bBoard& b,
        bMoveList& ml, bScore nValueAtNullMove,
        depth_t const nDepth)
{
  adjustMaxSearchedDepth(nDepth);
  CheckIfAbortingSearch();
 
  bScore terminalScore = RetrieveBoardEvaluation(b);
 
  if (bSearchScore::realScore(terminalScore) > bSearchScore::realScore(nValueAtNullMove)) {
    DEBUG_sendInfoSearching(b, nDepth, "st sc better than nullmove ("
            + belofte::to_string(nValueAtNullMove)
            + ") -- early cut off", terminalScore);
    return terminalScore;
  }
 
  movenum_t n_moves = ml.generateMoves(b);
  if (!ml.getNumberOfQSMoves()) {
    /// @todo can be no moves position because of mate
    DEBUG_sendInfoSearching(b, nDepth, "dead position (static eval)", terminalScore);
    return terminalScore;
  }
 
  DEBUG_sendInfoSearching(b, nDepth, "(static eval)", terminalScore);
 
  depth_t nNewDepth = nDepth + 1;
  bSearchScore bestscore(terminalScore);
  ml.clearScores();
  for (movenum_t moveid = 1; moveid <= n_moves; ++moveid) {
    bMove m(ml[moveid]);
    if (m.isNonSilent() || m.isCheck()) {
      sendInfoCurrMove(b, nDepth, m, moveid);
      bBoard chldbrd(b, m);
      chldbrd.applyMove(m);
      ++m_nonleafnodes;
      bMoveList chldML;
      bSearchScore chldscore(-Quiescence(chldbrd, chldML, -nValueAtNullMove, nNewDepth));
      ml.setScoreOfMove(moveid, chldscore.getScore());
      if (chldscore.improvesOn(bestscore)) {
        b.setVariation(chldbrd);
        bestscore = chldscore.getScore();
        /// @todo first capture will always be better
        if (chldscore.improvesOn(nValueAtNullMove)) {
          DEBUG_sendInfoSearching(b, nDepth, "better than nullmove ("
                  + belofte::to_string(nValueAtNullMove)
                  + ") -- cut-off", chldscore.getScore());
          return chldscore.getScore();
        }
      }
    }
  }
 
  DEBUG_sendInfoSearching(b, nDepth, "(return best)", bestscore.getScore());
  return bestscore.getScore();
}
 
//-----------------------------------------------------------------------
 
// eof