/// <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);
}