/// <summary>
/// Find the best move for a player using alpha-beta
/// </summary>
/// <param name="board"> Chess board</param>
/// <param name="searchMode"> Search mode</param>
/// <param name="ePlayer"> Player doing the move</param>
/// <param name="moveList"> Move list</param>
/// <param name="arrIndex"> Order of evaluation of the moves</param>
/// <param name="posInfo"> Information about pieces attacks</param>
/// <param name="moveBest"> Best move found</param>
/// <param name="iPermCount"> Total permutation evaluated</param>
/// <param name="iCacheHit"> Number of moves found in the translation table cache</param>
/// <param name="iMaxDepth"> Maximum depth to use</param>
/// <returns>
/// true if a move has been found
/// </returns>
protected override bool FindBestMove(ChessBoard board,
SearchMode searchMode,
ChessBoard.PlayerE ePlayer,
List <Move> moveList,
int[] arrIndex,
ChessBoard.PosInfoS posInfo,
ref Move moveBest,
out int iPermCount,
out int iCacheHit,
out int iMaxDepth)
{
bool bRetVal = false;
bool bMultipleThread;
bool bUseTransTable;
ChessBoard[] arrBoard;
Task <AlphaBetaResult>[] taskArray;
List <Move>[] arrMoveList;
AlphaBetaResult alphaBetaRes;
ChessBoard.PosInfoS posInfoWhite;
ChessBoard.PosInfoS posInfoBlack;
int iAlpha;
int iBeta;
int iThreadCount;
//TODO Enable transposition table when bug on 3 repetition move draw will be found.
if (ePlayer == ChessBoard.PlayerE.White)
{
posInfoWhite = posInfo;
posInfoBlack = ChessBoard.s_posInfoNull;
}
else
{
posInfoWhite = ChessBoard.s_posInfoNull;
posInfoBlack = posInfo;
}
searchMode.m_eOption &= ~SearchMode.OptionE.UseTransTable;
bUseTransTable = (searchMode.m_eOption.HasFlag(SearchMode.OptionE.UseTransTable));
iCacheHit = 0;
iMaxDepth = 0;
iPermCount = 0;
iAlpha = -10000000;
iBeta = +10000000;
bMultipleThread = (searchMode.m_eThreadingMode == SearchMode.ThreadingModeE.OnePerProcessorForSearch);
iThreadCount = System.Environment.ProcessorCount;
if (bMultipleThread && iThreadCount < 2)
{
bMultipleThread = false; // No reason to go with multi-threading if only one processor
}
if (bMultipleThread)
{
arrBoard = new ChessBoard[iThreadCount];
arrMoveList = new List <Move> [iThreadCount];
taskArray = new Task <AlphaBetaResult> [iThreadCount];
for (int iIndex = 0; iIndex < iThreadCount; iIndex++)
{
arrBoard[iIndex] = board.Clone();
arrMoveList[iIndex] = new List <Move>(moveList.Count / iThreadCount + 1);
for (int iStep = iIndex; iStep < moveList.Count; iStep += iThreadCount)
{
arrMoveList[iIndex].Add(moveList[arrIndex[iStep]]);
}
}
for (int iIndex = 0; iIndex < iThreadCount; iIndex++)
{
taskArray[iIndex] = Task <AlphaBetaResult> .Factory.StartNew((param) => {
int iStep = (int)param;
return(FindBestMoveUsingAlphaBetaAsync(arrBoard[iStep],
searchMode,
ePlayer,
iStep,
arrMoveList[iStep],
posInfoWhite,
posInfoBlack,
moveList.Count,
iAlpha,
iBeta));
}, iIndex);
}
iMaxDepth = 999;
for (int iStep = 0; iStep < iThreadCount; iStep++)
{
alphaBetaRes = taskArray[iStep].Result;
if (alphaBetaRes.movePosBest.StartPos != 255)
{
iPermCount += alphaBetaRes.iPermCount;
iMaxDepth = Math.Min(iMaxDepth, alphaBetaRes.iMaxDepth);
if (bUseTransTable)
{
iCacheHit += TransTable.GetTransTable(iStep).CacheHit;
}
if (alphaBetaRes.iPts > iAlpha)
{
iAlpha = alphaBetaRes.iPts;
moveBest = alphaBetaRes.movePosBest;
bRetVal = true;
}
}
}
if (iMaxDepth == 999)
{
iMaxDepth = -1;
}
}
else
{
ChessBoard chessBoardTmp;
List <Move> moveListTmp;
chessBoardTmp = board.Clone();
moveListTmp = new List <Move>(moveList.Count);
for (int iIndex = 0; iIndex < moveList.Count; iIndex++)
{
moveListTmp.Add(moveList[arrIndex[iIndex]]);
}
alphaBetaRes = FindBestMoveUsingAlphaBetaAsync(chessBoardTmp,
searchMode,
ePlayer,
0, // ThreadId
moveListTmp,
posInfoWhite,
posInfoBlack,
moveList.Count,
iAlpha,
iBeta);
iPermCount = alphaBetaRes.iPermCount;
iMaxDepth = alphaBetaRes.iMaxDepth;
if (alphaBetaRes.movePosBest.StartPos != 255)
{
if (bUseTransTable)
{
iCacheHit += TransTable.GetTransTable(0).CacheHit;
}
moveBest = alphaBetaRes.movePosBest;
bRetVal = true;
}
}
return(bRetVal);
}
/// <summary>
/// Find the best move for a player using alpha-beta in a secondary thread
/// </summary>
/// <param name="board"> Chess board</param>
/// <param name="searchMode"> Search mode</param>
/// <param name="ePlayer"> Color doing the move</param>
/// <param name="iThreadId"> Thread Id (0-n)</param>
/// <param name="moveList"> List of move to try</param>
/// <param name="posInfoWhite"> Information about pieces attacks for the white</param>
/// <param name="posInfoBlack"> Information about pieces attacks for the black</param>
/// <param name="iTotalMoveCount"> Total number of moves</param>
/// <param name="iAlpha"> Alpha bound</param>
/// <param name="iBeta"> Beta bound</param>
/// <returns>
/// Points
/// </returns>
private AlphaBetaResult FindBestMoveUsingAlphaBetaAsync(ChessBoard board,
SearchMode searchMode,
ChessBoard.PlayerE ePlayer,
int iThreadId,
List <Move> moveList,
ChessBoard.PosInfoS posInfoWhite,
ChessBoard.PosInfoS posInfoBlack,
int iTotalMoveCount,
int iAlpha,
int iBeta)
{
AlphaBetaResult resRetVal;
DateTime dtTimeOut;
int iDepth;
int iPermCountAtLevel;
int iPoint;
int iBestMoveIndex;
int iDepthLimit;
int[] arrPoints;
System.Threading.ThreadPriority eThreadPriority;
TransTable transTable;
bool bTimeOut;
bool bIterativeDepthFirst;
resRetVal = new AlphaBetaResult();
eThreadPriority = System.Threading.Thread.CurrentThread.Priority;
System.Threading.Thread.CurrentThread.Priority = System.Threading.ThreadPriority.BelowNormal;
if ((searchMode.m_eOption & SearchMode.OptionE.UseTransTable) != 0)
{
transTable = TransTable.GetTransTable(iThreadId);
transTable.Reset();
}
else
{
transTable = null;
}
bIterativeDepthFirst = (searchMode.m_eOption.HasFlag(SearchMode.OptionE.UseIterativeDepthSearch));
resRetVal.movePosBest.StartPos = 255;
resRetVal.movePosBest.EndPos = 255;
resRetVal.movePosBest.OriginalPiece = ChessBoard.PieceE.None;
resRetVal.movePosBest.Type = Move.TypeE.Normal;
try {
resRetVal.iPermCount = 0;
if (searchMode.m_iSearchDepth == 0 || bIterativeDepthFirst)
{
dtTimeOut = (bIterativeDepthFirst) ? DateTime.MaxValue : DateTime.Now + TimeSpan.FromSeconds(searchMode.m_iTimeOutInSec);
iDepthLimit = (bIterativeDepthFirst) ? searchMode.m_iSearchDepth : 999;
iDepth = 1;
resRetVal.iPts = FindBestMoveUsingAlphaBetaAtDepth(board,
searchMode,
ePlayer,
moveList,
posInfoWhite,
posInfoBlack,
iTotalMoveCount,
iDepth,
iAlpha,
iBeta,
transTable,
DateTime.MaxValue,
out iPermCountAtLevel,
out iBestMoveIndex,
out bTimeOut,
out arrPoints);
if (iBestMoveIndex != -1)
{
resRetVal.movePosBest = moveList[iBestMoveIndex];
}
resRetVal.iPermCount += iPermCountAtLevel;
resRetVal.iMaxDepth = iDepth;
while (DateTime.Now < dtTimeOut && !m_bCancelSearch && !bTimeOut && iDepth < iDepthLimit)
{
moveList = SortMoveList(moveList, arrPoints);
iDepth++;
iPoint = FindBestMoveUsingAlphaBetaAtDepth(board,
searchMode,
ePlayer,
moveList,
posInfoWhite,
posInfoBlack,
iTotalMoveCount,
iDepth,
iAlpha,
iBeta,
transTable,
dtTimeOut,
out iPermCountAtLevel,
out iBestMoveIndex,
out bTimeOut,
out arrPoints);
if (!bTimeOut)
{
if (iBestMoveIndex != -1)
{
resRetVal.movePosBest = moveList[iBestMoveIndex];
}
resRetVal.iPermCount += iPermCountAtLevel;
resRetVal.iMaxDepth = iDepth;
resRetVal.iPts = iPoint;
}
}
}
else
{
resRetVal.iMaxDepth = searchMode.m_iSearchDepth;
resRetVal.iPts = FindBestMoveUsingAlphaBetaAtDepth(board,
searchMode,
ePlayer,
moveList,
posInfoWhite,
posInfoBlack,
iTotalMoveCount,
resRetVal.iMaxDepth,
iAlpha,
iBeta,
transTable,
DateTime.MaxValue,
out resRetVal.iPermCount,
out iBestMoveIndex,
out bTimeOut,
out arrPoints);
if (iBestMoveIndex != -1)
{
resRetVal.movePosBest = moveList[iBestMoveIndex];
}
}
} finally {
System.Threading.Thread.CurrentThread.Priority = eThreadPriority;
}
return(resRetVal);
}
/// <summary>
/// Minimum/maximum depth first search
/// </summary>
/// <param name="board"> Chess board</param>
/// <param name="searchMode"> Search mode</param>
/// <param name="ePlayer"> Player 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 board, SearchMode searchMode, ChessBoard.PlayerE ePlayer, int iDepth, int iWhiteMoveCount, int iBlackMoveCount, ref int iPermCount)
{
int iRetVal;
int iMoveCount;
int iPts;
List <Move> moveList;
ChessBoard.RepeatResultE eResult;
if (board.IsEnoughPieceForCheckMate())
{
if (iDepth == 0 || m_bCancelSearch)
{
iRetVal = (ePlayer == ChessBoard.PlayerE.Black) ? -board.Points(searchMode, ePlayer, 0, iWhiteMoveCount - iBlackMoveCount, ChessBoard.s_posInfoNull, ChessBoard.s_posInfoNull) :
board.Points(searchMode, ePlayer, 0, iWhiteMoveCount - iBlackMoveCount, ChessBoard.s_posInfoNull, ChessBoard.s_posInfoNull);
iPermCount++;
}
else
{
moveList = board.EnumMoveList(ePlayer);
iMoveCount = moveList.Count;
if (ePlayer == ChessBoard.PlayerE.White)
{
iWhiteMoveCount = iMoveCount;
}
else
{
iBlackMoveCount = iMoveCount;
}
if (iMoveCount == 0)
{
if (board.IsCheck(ePlayer))
{
iRetVal = -1000000 - iDepth;
}
else
{
iRetVal = 0; // Draw
}
}
else
{
iRetVal = Int32.MinValue;
foreach (Move move in moveList)
{
eResult = board.DoMoveNoLog(move);
if (eResult == ChessBoard.RepeatResultE.NoRepeat)
{
iPts = -MinMax(board,
searchMode,
(ePlayer == ChessBoard.PlayerE.Black) ? ChessBoard.PlayerE.White : ChessBoard.PlayerE.Black,
iDepth - 1,
iWhiteMoveCount,
iBlackMoveCount,
ref iPermCount);
}
else
{
iPts = 0;
}
board.UndoMoveNoLog(move);
if (iPts > iRetVal)
{
iRetVal = iPts;
}
}
}
}
}
else
{
iRetVal = 0;
}
return(iRetVal);
}
/// <summary>
/// Find the best move for a player using alpha-beta for a given depth
/// </summary>
/// <param name="board"> Chess board</param>
/// <param name="searchMode"> Search mode</param>
/// <param name="ePlayer"> Color doing the move</param>
/// <param name="moveList"> List of move to try</param>
/// <param name="posInfoWhite"> Information about pieces attacks for the white</param>
/// <param name="posInfoBlack"> Information about pieces attacks for the black</param>
/// <param name="iTotalMoveCount"> Total list of moves</param>
/// <param name="iDepth"> Maximum depth</param>
/// <param name="iAlpha"> Alpha bound</param>
/// <param name="iBeta"> Beta bound</param>
/// <param name="transTable"> Transposition table or null if not using one</param>
/// <param name="dtTimeOut"> Time limit (DateTime.MaxValue for no time limit)</param>
/// <param name="iPermCount"> Total permutation evaluated</param>
/// <param name="iBestMoveIndex"> Index of the best move</param>
/// <param name="bTimeOut"> Return true if time out</param>
/// <param name="arrPoints"> Returns point of each move in move list</param>
/// <returns>
/// Points
/// </returns>
private int FindBestMoveUsingAlphaBetaAtDepth(ChessBoard board,
SearchMode searchMode,
ChessBoard.PlayerE ePlayer,
List <Move> moveList,
ChessBoard.PosInfoS posInfoWhite,
ChessBoard.PosInfoS posInfoBlack,
int iTotalMoveCount,
int iDepth,
int iAlpha,
int iBeta,
TransTable transTable,
DateTime dtTimeOut,
out int iPermCount,
out int iBestMoveIndex,
out bool bTimeOut,
out int[] arrPoints)
{
int iRetVal = -10000000;
int iWhiteMoveCount;
int iBlackMoveCount;
int iMoveCount;
int iIndex;
int iPts;
Move move;
AlphaBetaInfo abInfo;
ChessBoard.RepeatResultE eResult;
bTimeOut = false;
abInfo = new AlphaBetaInfo();
abInfo.m_arrMove = new Move[iDepth];
abInfo.m_iPermCount = 0;
abInfo.m_dtTimeOut = dtTimeOut;
abInfo.m_transTable = transTable;
abInfo.m_iMaxDepth = iDepth;
abInfo.m_searchMode = searchMode;
abInfo.m_posInfoWhite = posInfoWhite;
abInfo.m_posInfoBlack = posInfoBlack;
iBestMoveIndex = -1;
arrPoints = new int[moveList.Count];
if (ePlayer == ChessBoard.PlayerE.White)
{
iWhiteMoveCount = iTotalMoveCount;
iBlackMoveCount = 0;
}
else
{
iWhiteMoveCount = 0;
iBlackMoveCount = iTotalMoveCount;
}
iMoveCount = moveList.Count;
iIndex = 0;
iRetVal = iAlpha;
while (iIndex < iMoveCount && !bTimeOut)
{
move = moveList[iIndex];
eResult = board.DoMoveNoLog(move);
abInfo.m_arrMove[iDepth - 1] = move;
if (eResult == ChessBoard.RepeatResultE.NoRepeat)
{
iPts = -AlphaBeta(board,
(ePlayer == ChessBoard.PlayerE.Black) ? ChessBoard.PlayerE.White : ChessBoard.PlayerE.Black,
iDepth - 1,
-iBeta,
-iRetVal,
iWhiteMoveCount,
iBlackMoveCount,
abInfo);
}
else
{
iPts = 0;
}
arrPoints[iIndex] = iPts;
board.UndoMoveNoLog(move);
if (iPts == Int32.MinValue)
{
iRetVal = iPts;
bTimeOut = true;
}
else
{
if (iPts > iRetVal)
{
TraceSearch(iDepth, ePlayer, move, iPts);
iRetVal = iPts;
iBestMoveIndex = iIndex;
}
}
iIndex++;
}
iPermCount = abInfo.m_iPermCount;
return(iRetVal);
}
/// <summary>
/// Gets the search mode from the setting
/// </summary>
/// <returns></returns>
public SearchMode GetSearchMode()
{
SearchMode searchModeRetVal;
Book bookComputer;
SearchMode.OptionE eOption;
SearchMode.ThreadingModeE eThreadingMode;
int iTimeOutInSec;
eOption = SearchMode.OptionE.UseAlphaBeta | SearchMode.OptionE.UseIterativeDepthSearch | SearchMode.OptionE.UseTransTable;
eThreadingMode = SearchMode.ThreadingModeE.OnePerProcessorForSearch;
iTimeOutInSec = 0;
switch (ActiveComputerBookMode)
{
case BookModeE.NoBook:
bookComputer = null;
break;
case BookModeE.Unrated:
bookComputer = SearchMode.BookUnrated;
break;
default:
bookComputer = SearchMode.Book2500;
break;
}
switch (DifficultyLevel)
{
case DifficultyLevelE.VeryEasy:
searchModeRetVal = new SearchMode(new BoardEvaluationWeak(),
new BoardEvaluationWeak(),
eOption,
eThreadingMode,
2 /*iSearchDepth*/,
iTimeOutInSec,
SearchMode.RandomModeE.On,
SearchMode.Book2500,
bookComputer);
break;
case DifficultyLevelE.Easy:
searchModeRetVal = new SearchMode(new BoardEvaluationBasic(),
new BoardEvaluationBasic(),
eOption,
eThreadingMode,
2 /*iSearchDepth*/,
iTimeOutInSec,
SearchMode.RandomModeE.On,
SearchMode.Book2500,
bookComputer);
break;
case DifficultyLevelE.Intermediate:
searchModeRetVal = new SearchMode(new BoardEvaluationBasic(),
new BoardEvaluationBasic(),
eOption,
eThreadingMode,
4 /*iSearchDepth*/,
iTimeOutInSec,
SearchMode.RandomModeE.On,
SearchMode.Book2500,
bookComputer);
break;
case DifficultyLevelE.Hard:
searchModeRetVal = new SearchMode(new BoardEvaluationBasic(),
new BoardEvaluationBasic(),
eOption,
eThreadingMode,
4 /*iSearchDepth*/,
iTimeOutInSec,
SearchMode.RandomModeE.On,
SearchMode.Book2500,
bookComputer);
break;
case DifficultyLevelE.VeryHard:
searchModeRetVal = new SearchMode(WhiteBoardEvaluation,
BlackBoardEvaluation,
eOption,
eThreadingMode,
6 /*iSearchDepth*/,
iTimeOutInSec,
SearchMode.RandomModeE.On,
SearchMode.Book2500,
bookComputer);
break;
default:
searchModeRetVal = new SearchMode(WhiteBoardEvaluation,
BlackBoardEvaluation,
Option,
ThreadingMode,
SearchDepth,
TimeOutInSec,
RandomMode,
SearchMode.Book2500,
bookComputer);
break;
}
return(searchModeRetVal);
}