// Store entry into TTable
public void storeTTable(UInt64 key, TTEntry entry)
{
int index = (int) (key % Constants.TT_SIZE);
// If entry in bucket has same hash key, then replace
for (int i = index; i < index + Constants.BUCKET_SIZE; i++) {
if (this.transpositionTable[i].key == key) {
this.transpositionTable[i] = entry;
return;
}
}
// If there is an empty spot in the bucket, then store it there
for (int i = index; i < index + Constants.BUCKET_SIZE; i++) {
if (this.transpositionTable[i].key == 0) {
this.transpositionTable[i] = entry;
return;
}
}
// If all spots full, then replace entry with lowest depth
int shallowestDepth = Constants.INF;
int indexOfShallowestEntry = -1;
for (int i = index; i < index + Constants.BUCKET_SIZE; i++) {
if (this.transpositionTable[i].depth < shallowestDepth) {
shallowestDepth = this.transpositionTable[i].depth;
indexOfShallowestEntry = i;
}
}
this.transpositionTable[indexOfShallowestEntry] = entry;
}
// Store entry into TTable
public void storeTTable(UInt64 key, TTEntry entry)
{
int index = (int)(key % Constants.TT_SIZE);
// If entry in bucket has same hash key, then replace
for (int i = index; i < index + Constants.BUCKET_SIZE; i++)
{
if (this.transpositionTable[i].key == key)
{
this.transpositionTable[i] = entry;
return;
}
}
// If there is an empty spot in the bucket, then store it there
for (int i = index; i < index + Constants.BUCKET_SIZE; i++)
{
if (this.transpositionTable[i].key == 0)
{
this.transpositionTable[i] = entry;
return;
}
}
// If all spots full, then replace entry with lowest depth
int shallowestDepth = Constants.INF;
int indexOfShallowestEntry = -1;
for (int i = index; i < index + Constants.BUCKET_SIZE; i++)
{
if (this.transpositionTable[i].depth < shallowestDepth)
{
shallowestDepth = this.transpositionTable[i].depth;
indexOfShallowestEntry = i;
}
}
this.transpositionTable[indexOfShallowestEntry] = entry;
}
public static int solve(int nodeType, Position inputBoard, int ply, int alpha, int beta, int depth)
{
// return score for terminal state
if (inputBoard.HasWon(inputBoard.arrayOfBitboard[(inputBoard.nPlies - 1) & 1]))
{
return(-Constants.WIN + ply);
}
else if (inputBoard.nPlies == 42)
{
Debug.Assert(depth == 0);
return(Constants.DRAW);
}
// "Mate" distance pruning
alpha = Math.Max(ply - Constants.WIN, alpha);
beta = Math.Min(Constants.WIN - (ply + 1), beta);
if (alpha >= beta)
{
return(alpha);
}
// probe transposition table
TTEntry entry = Solve.TranspositionTable.probeTTable(inputBoard.key);
// If entry has a flag type, then key will match (probe function performs check), only empty entries will have a key that doesn't match
if (entry.flag == Constants.EXACT ||
entry.flag == Constants.L_BOUND && entry.evaluationScore >= beta ||
entry.flag == Constants.U_BOUND && entry.evaluationScore <= alpha)
{
Debug.Assert(entry.key == inputBoard.key && entry.depth == depth);
// Only exact and lower bound entries can satisfy this condition and they all have valid moves stored, so don't have to check if move == -1 (only the case with upper bound entries)
if (entry.evaluationScore >= beta)
{
Debug.Assert(entry.move != Constants.NO_MOVE);
updateKillers(entry.move, ply);
}
return(entry.evaluationScore);
}
// hash move, if entry is exact then code will not be reached and if entry is an upper bound then it will have no move
int hashMove = (entry.flag == Constants.L_BOUND && entry.evaluationScore < beta) ? entry.move : Constants.NO_MOVE;
int bestScore = -Constants.INF;
int movesMade = 0;
int numberOfMoves = 0, moveIndex = 0;
bool raisedAlpha = false;
Move[] moveList = moveGenerator(ply, hashMove, ref numberOfMoves, inputBoard);
int bestMove = Constants.NO_MOVE;
// loop through all moves
while (true)
{
int move = getNextMove(numberOfMoves, ref moveIndex, moveList);
if (move == Constants.NO_MOVE)
{
break;
}
inputBoard.MakeMove(move);
int score = -solve(Constants.NON_ROOT, inputBoard, ply + 1, -beta, -alpha, depth - 1);
inputBoard.UnmakeMove();
nodesVisited++;
movesMade++;
if (score >= beta)
{
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.L_BOUND, depth, score, move);
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
updateKillers(move, ply);
updateHistory(depth, ply, move);
if (movesMade == 1)
{
fh1++;
}
else
{
fh++;
}
return(score);
}
else if (score > bestScore)
{
bestScore = score;
bestMove = move;
if (score > alpha)
{
alpha = score;
raisedAlpha = true;
}
}
}
// Store in transposition table
if (raisedAlpha)
{
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.EXACT, depth, alpha, bestMove);
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
}
else
{
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.U_BOUND, depth, bestScore, Constants.NO_MOVE); // no best move
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
}
return(bestScore);
}
public static int solve(int nodeType, Position inputBoard, int ply, int alpha, int beta, int depth)
{
// return score for terminal state
if (inputBoard.HasWon(inputBoard.arrayOfBitboard[(inputBoard.nPlies - 1) & 1])) {
return -Constants.WIN + ply;
} else if (inputBoard.nPlies == 42) {
Debug.Assert(depth == 0);
return Constants.DRAW;
}
// "Mate" distance pruning
//if (nodeType != Constants.ROOT) {
alpha = Math.Max(ply-Constants.WIN, alpha);
beta = Math.Min(Constants.WIN - (ply + 1), beta);
if (alpha >= beta) {
return alpha;
}
//}
// probe transposition table
TTEntry entry = Solve.TranspositionTable.probeTTable(inputBoard.key);
// If entry has a flag type, then key will match (probe function performs check), only empty entries will have a key that doesn't match
if (entry.flag == Constants.EXACT
|| entry.flag == Constants.L_BOUND && entry.evaluationScore >= beta
|| entry.flag == Constants.U_BOUND && entry.evaluationScore <= alpha) {
Debug.Assert(entry.key == inputBoard.key && entry.depth == depth);
// Only exact and lower bound entries can satisfy this condition and they all have valid moves stored, so don't have to check if move == -1 (only the case with upper bound entries)
if (entry.evaluationScore >= beta) {
Debug.Assert(entry.move != Constants.NO_MOVE);
updateKillers(entry.move, ply);
}
return entry.evaluationScore;
}
// hash move, if entry is exact then code will not be reached and if entry is an upper bound then it will have no move
int hashMove = (entry.flag == Constants.L_BOUND && entry.evaluationScore < beta) ? entry.move : Constants.NO_MOVE;
int bestScore = -Constants.INF;
int movesMade = 0;
bool raisedAlpha = false;
movePicker mPicker = new movePicker(inputBoard, ply, hashMove);
int bestMove = Constants.NO_MOVE;
// loop through all moves
while (true) {
int move = mPicker.getNextMove();
if (move == Constants.NO_MOVE) {
break;
}
inputBoard.MakeMove(move);
int score = -solve(Constants.NON_ROOT, inputBoard, ply + 1, -beta, -alpha, depth - 1);
inputBoard.UnmakeMove();
nodesVisited++;
movesMade++;
if (score >= beta) {
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.L_BOUND, depth, score, move);
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
updateKillers(move, ply);
updateHistory(depth, ply, move);
if (movesMade == 1) {
fh1++;
} else {
fh++;
}
return score;
} else if (score > bestScore) {
bestScore = score;
bestMove = move;
if (score > alpha) {
alpha = score;
raisedAlpha = true;
}
}
}
// Store in transposition table
if (raisedAlpha) {
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.EXACT, depth, alpha, bestMove);
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
} else {
TTEntry newEntry = new TTEntry(inputBoard.key, Constants.U_BOUND, depth, bestScore, Constants.NO_MOVE); // no best move
Solve.TranspositionTable.storeTTable(inputBoard.key, newEntry);
}
return bestScore;
}