/// <summary>
/// Alpha Beta pruning function.
/// </summary>
/// <param name="chessBoard"> Chess board</param>
/// <param name="ePlayerColor"> Color doing the move</param>
/// <param name="iDepth"> Actual search depth</param>
/// <param name="iAlpha"> Alpha limit</param>
/// <param name="iBeta"> Beta limit</param>
/// <param name="iWhiteMoveCount"> Number of moves white can do</param>
/// <param name="iBlackMoveCount"> Number of moves black can do</param>
/// <param name="abInfo"> Supplemental information</param>
/// <returns>
/// Points to give for this move or Int32.MinValue for timed out
/// </returns>
private int AlphaBeta(ChessBoard chessBoard, ChessBoard.PlayerColorE ePlayerColor, int iDepth, int iAlpha, int iBeta, int iWhiteMoveCount, int iBlackMoveCount, AlphaBetaInfo abInfo)
{
int iRetVal;
List<ChessBoard.MovePosS> moveList;
int iPts;
int iMoveCount;
ChessBoard.PosInfoS posInfo;
TransEntryTypeE eType = TransEntryTypeE.Alpha;
ChessBoard.BoardStateMaskE eBoardExtraInfo;
ChessBoard.RepeatResultE eResult;
if (abInfo.m_dtTimeOut != DateTime.MaxValue && DateTime.Now >= abInfo.m_dtTimeOut) {
iRetVal = Int32.MinValue; // Time out!
} else if (chessBoard.IsEnoughPieceForCheckMate()) {
eBoardExtraInfo = chessBoard.ComputeBoardExtraInfo(ePlayerColor, true);
iRetVal = (abInfo.m_transTable != null) ? abInfo.m_transTable.ProbeEntry(chessBoard.CurrentZobristKey, eBoardExtraInfo, iDepth, iAlpha, iBeta) : Int32.MaxValue;
if (iRetVal == Int32.MaxValue) {
if (iDepth == 0 || m_bCancelSearch) {
iRetVal = chessBoard.Points(abInfo.m_searchMode, ePlayerColor, abInfo.m_iMaxDepth - iDepth, iWhiteMoveCount - iBlackMoveCount, abInfo.m_posInfoWhite, abInfo.m_posInfoBlack);
if (ePlayerColor == ChessBoard.PlayerColorE.Black) {
iRetVal = -iRetVal;
}
abInfo.m_iPermCount++;
if (abInfo.m_transTable != null) {
abInfo.m_transTable.RecordEntry(chessBoard.CurrentZobristKey, eBoardExtraInfo, iDepth, iRetVal, TransEntryTypeE.Exact);
}
} else {
moveList = chessBoard.EnumMoveList(ePlayerColor, true, out posInfo);
iMoveCount = moveList.Count;
if (ePlayerColor == ChessBoard.PlayerColorE.White) {
iWhiteMoveCount = iMoveCount;
abInfo.m_posInfoWhite = posInfo;
} else {
iBlackMoveCount = iMoveCount;
abInfo.m_posInfoBlack = posInfo;
}
if (iMoveCount == 0) {
if (chessBoard.IsCheck(ePlayerColor)) {
iRetVal = -1000000 - iDepth;
} else {
iRetVal = 0; // Draw
}
if (abInfo.m_transTable != null) {
abInfo.m_transTable.RecordEntry(chessBoard.CurrentZobristKey, eBoardExtraInfo, iDepth, iRetVal, TransEntryTypeE.Exact);
}
} else {
iRetVal = iAlpha;
foreach (ChessBoard.MovePosS move in moveList) {
eResult = chessBoard.DoMoveNoLog(move);
abInfo.m_arrMovePos[iDepth - 1] = move;
if (eResult == ChessBoard.RepeatResultE.NoRepeat) {
iPts = -AlphaBeta(chessBoard,
(ePlayerColor == ChessBoard.PlayerColorE.Black) ? ChessBoard.PlayerColorE.White : ChessBoard.PlayerColorE.Black,
iDepth - 1,
-iBeta,
-iRetVal,
iWhiteMoveCount,
iBlackMoveCount,
abInfo);
} else {
iPts = 0;
}
chessBoard.UndoMoveNoLog(move);
if (iPts == Int32.MinValue) {
iRetVal = iPts;
break;
} else {
if (iPts > iRetVal) {
iRetVal = iPts;
eType = TransEntryTypeE.Exact;
}
if (iRetVal >= iBeta) {
iRetVal = iBeta;
eType = TransEntryTypeE.Beta;
break;
}
}
}
if (abInfo.m_transTable != null && iRetVal != Int32.MinValue) {
abInfo.m_transTable.RecordEntry(chessBoard.CurrentZobristKey, eBoardExtraInfo, iDepth, iRetVal, eType);
}
}
}
}
} else {
iRetVal = 0;
}
return(iRetVal);
}
/// <summary>
/// Minimum/maximum depth first search
/// </summary>
/// <param name="chessBoard"> Chess board</param>
/// <param name="searchMode"> Search mode</param>
/// <param name="ePlayerColor"> Color doing the move</param>
/// <param name="iDepth"> Actual search depth</param>
/// <param name="iWhiteMoveCount"> Number of moves white can do</param>
/// <param name="iBlackMoveCount"> Number of moves black can do</param>
/// <param name="iPermCount"> Total permutation evaluated</param>
/// <returns>
/// Points to give for this move
/// </returns>
private int MinMax(ChessBoard chessBoard, SearchMode searchMode, ChessBoard.PlayerColorE ePlayerColor, int iDepth, int iWhiteMoveCount, int iBlackMoveCount, ref int iPermCount)
{
int iRetVal;
int iMoveCount;
int iPts;
List<ChessBoard.MovePosS> moveList;
ChessBoard.RepeatResultE eResult;
if (chessBoard.IsEnoughPieceForCheckMate()) {
if (iDepth == 0 || m_bCancelSearch) {
iRetVal = (ePlayerColor == ChessBoard.PlayerColorE.Black) ? -chessBoard.Points(searchMode, ePlayerColor, 0, iWhiteMoveCount - iBlackMoveCount, ChessBoard.s_posInfoNull, ChessBoard.s_posInfoNull) :
chessBoard.Points(searchMode, ePlayerColor, 0, iWhiteMoveCount - iBlackMoveCount, ChessBoard.s_posInfoNull, ChessBoard.s_posInfoNull);
iPermCount++;
} else {
moveList = chessBoard.EnumMoveList(ePlayerColor);
iMoveCount = moveList.Count;
if (ePlayerColor == ChessBoard.PlayerColorE.White) {
iWhiteMoveCount = iMoveCount;
} else {
iBlackMoveCount = iMoveCount;
}
if (iMoveCount == 0) {
if (chessBoard.IsCheck(ePlayerColor)) {
iRetVal = -1000000 - iDepth;
} else {
iRetVal = 0; // Draw
}
} else {
iRetVal = Int32.MinValue;
foreach (ChessBoard.MovePosS move in moveList) {
eResult = chessBoard.DoMoveNoLog(move);
if (eResult == ChessBoard.RepeatResultE.NoRepeat) {
iPts = -MinMax(chessBoard,
searchMode,
(ePlayerColor == ChessBoard.PlayerColorE.Black) ? ChessBoard.PlayerColorE.White : ChessBoard.PlayerColorE.Black,
iDepth - 1,
iWhiteMoveCount,
iBlackMoveCount,
ref iPermCount);
} else {
iPts = 0;
}
chessBoard.UndoMoveNoLog(move);
if (iPts > iRetVal) {
iRetVal = iPts;
}
}
}
}
} else {
iRetVal = 0;
}
return(iRetVal);
}