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Better PV output
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Plan B committed Nov 25, 2018
1 parent 3881d25 commit 9d39832
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Showing 2 changed files with 47 additions and 35 deletions.
60 changes: 31 additions & 29 deletions src/search.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ std::vector<std::pair<Move, int>> scoreNoisyMoves(const Board& b, const std::vec
return scoredMoves;
}

int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bool allowNull = true) {
int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, Move (&ppv)[MAX_PLY], bool allowNull = true) {
if (timeOver(si)) return alpha;

bool isRoot = (!ply);
Expand Down Expand Up @@ -134,6 +134,9 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
}
}

Move pv[MAX_PLY];
for (auto& m : pv) m = NO_MOVE;

bool isInCheck = inCheck(b, b.turn);

if (depth <= 0) {
Expand All @@ -144,7 +147,7 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
}
else {
// Drop into qsearch
int qscore = qsearch(b, ply, alpha, beta, si);
int qscore = qsearch(b, ply, alpha, beta, si, pv);
return qscore;
}
}
Expand All @@ -166,7 +169,7 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
auto u = makeNullMove(b);
int nullMoveR = nullMoveBaseR + depth / 6;
nullMoveR = std::min(nullMoveR, 4);
score = -search(b, depth - 1 - nullMoveR, ply + 1, -beta, -beta + 1, si, false);
score = -search(b, depth - 1 - nullMoveR, ply + 1, -beta, -beta + 1, si, pv, false);
undoNullMove(b, u);
if (score >= beta) return score;
}
Expand Down Expand Up @@ -218,10 +221,10 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
if (isKiller) lateMoveR -= 1;

lateMoveR = std::max(0, std::min(lateMoveR, depth - 1)); // Do not drop directly into qsearch
score = -search(b, depth - lateMoveR - 1, ply + 1, -alpha - 1, -alpha, si);
score = -search(b, depth - lateMoveR - 1, ply + 1, -alpha - 1, -alpha, si, pv);
}

if (score > alpha) score = -search(b, depth - 1, ply + 1, -beta, -alpha, si);
if (score > alpha) score = -search(b, depth - 1, ply + 1, -beta, -alpha, si, pv);

undoMove(b, m, u);

Expand All @@ -238,7 +241,7 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
}

// Update history score
if (!isNoisy) historyMoves[b.turn][pieceType(b.squares[m.from])][m.to] += depth * depth;
if (!isNoisy && depth <= 12) historyMoves[b.turn][pieceType(b.squares[m.from])][m.to] += depth * depth;

// Update move ordering info
si.failHigh++;
Expand All @@ -251,6 +254,13 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
alpha = score;
bestMove = m;
TTFlag = TT_EXACT;

// Copy PV from child nodes
ppv[ply] = m;
for (int i = ply + 1; i < MAX_PLY; ++i) {
if (pv[i] == NO_MOVE) break;
ppv[i] = pv[i];
}
}
}

Expand All @@ -269,7 +279,7 @@ int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bo
return alpha;
}

int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si) {
int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si, Move (&ppv)[MAX_PLY]) {
if (timeOver(si)) return alpha;
if (ply > si.seldepth) si.seldepth = ply;

Expand All @@ -289,6 +299,9 @@ int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si) {
std::vector<std::pair<Move, int>> scoredNoisyMoves = scoreNoisyMoves(b, noisyMoves);
std::sort(scoredNoisyMoves.begin(), scoredNoisyMoves.end(), [](const auto& a, const auto& b) { return a.second > b.second; });

Move pv[MAX_PLY];
for (auto& m : pv) m = NO_MOVE;

for (int i = 0, size = scoredNoisyMoves.size(); i < size; ++i) {
Move m = scoredNoisyMoves[i].first;

Expand All @@ -304,13 +317,21 @@ int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si) {
continue;
}

int score = -qsearch(b, ply + 1, -beta, -alpha, si);
int score = -qsearch(b, ply + 1, -beta, -alpha, si, pv);
undoMove(b, m, u);

si.qnodes++;

if (score >= beta) return beta;
if (score > alpha) alpha = score;
if (score > alpha) {
alpha = score;

ppv[ply] = m;
for (int i = ply + 1; i < MAX_PLY; ++i) {
if (pv[i] == NO_MOVE) break;
ppv[i] = pv[i];
}
}
}
return alpha;
}
Expand Down Expand Up @@ -409,7 +430,7 @@ void iterativeDeepening(Board& b, SearchInfo& si, int timeLimit) {
si.reset();
si.depth = i;

int score = search(b, i, 0, alpha, beta, si);
int score = search(b, i, 0, alpha, beta, si, si.pv);
if (timeOver(si)) break;

if ((score <= alpha) || (score >= beta)) {
Expand All @@ -421,8 +442,6 @@ void iterativeDeepening(Board& b, SearchInfo& si, int timeLimit) {
}

si.print();
printPV(b, i);
std::cout << "\n";

research = false;
if (i >= aspirationMinDepth) {
Expand All @@ -434,21 +453,4 @@ void iterativeDeepening(Board& b, SearchInfo& si, int timeLimit) {
si = searchCache;
std::cout << "bestmove " << toNotation(si.bestMove) << "\n";
ageTT();
}

void printPV(Board b, int limit) {
int ply = 0;
std::cout << "pv ";
auto it = tt.find(b.key);
Move hashMove = (it != tt.end()) ? it->second.move : NO_MOVE;
while (hashMove != NO_MOVE) {
ply++;
makeMove(b, hashMove);
std::cout << toNotation(hashMove) << " ";
it = tt.find(b.key);
hashMove = (it != tt.end()) ? it->second.move : NO_MOVE;
// PV currently does not account for threefold repetition and will cycle hash moves
// We use a failsafe to prevent an infinite loop
if (ply > limit) break;
}
}
22 changes: 16 additions & 6 deletions src/search.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ struct SearchInfo {
Move bestMove = NO_MOVE;
double start = clock();
int limit = 0;
Move pv[MAX_PLY];

void operator=(const SearchInfo& si) {
depth = si.depth;
Expand All @@ -29,6 +30,10 @@ struct SearchInfo {
bestMove = si.bestMove;
start = si.start;
limit = si.limit;
for (int i = 0; i < MAX_PLY; ++i) {
if (si.pv[i] == NO_MOVE) break;
pv[i] = si.pv[i];
}
}

void initTime(int limitParam) {
Expand All @@ -45,6 +50,7 @@ struct SearchInfo {
failHigh = 0;
failHighFirst = 0;
bestMove = NO_MOVE;
for (auto& m : pv) m = NO_MOVE;
}

void print() {
Expand All @@ -56,7 +62,13 @@ struct SearchInfo {
std::cout << "mate " << (MATE_SCORE - abs(score)) / 2 + (score > 0);
}
std::cout << " depth " << depth << " seldepth " << seldepth << " nodes " << nodes + qnodes;
std::cout << " time " << (double)(clock() - start) / (CLOCKS_PER_SEC / 1000) << " ";
std::cout << " time " << (double)(clock() - start) / (CLOCKS_PER_SEC / 1000);
std::cout << " pv ";
for (const auto& m : pv) {
if (m == NO_MOVE) break;
std::cout << toNotation(m) << " ";
}
std::cout << "\n";
}
};

Expand All @@ -76,7 +88,7 @@ static constexpr int lateMoveMinDepth = 3;
static constexpr int lateMoveMinMove = 4;

static constexpr int lateMovePruningMaxDepth = 4;
static constexpr int lateMovePruningMove = 8;
static constexpr int lateMovePruningMove = 7;

static constexpr int hashMoveBonus = 500000;

Expand All @@ -103,15 +115,13 @@ std::vector<std::pair<Move, int>> scoreMoves(const Board& b, const std::vector<M
int scoreNoisyMove(const Board& b, const Move& m);
std::vector<std::pair<Move, int>> scoreNoisyMoves(const Board& b, const std::vector<Move>& moves);

int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, bool allowNull);
int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si);
int search(Board& b, int depth, int ply, int alpha, int beta, SearchInfo& si, Move(&ppv)[MAX_PLY], bool allowNull);
int qsearch(Board& b, int ply, int alpha, int beta, SearchInfo& si, Move (&ppv)[MAX_PLY]);

int staticExchangeEvaluation(const Board& b, const Move& m, int threshold = 0);
int SEEMoveVal(const Board& b, const Move& m);
int greatestTacticalGain(const Board& b);

void iterativeDeepening(Board& b, SearchInfo& si, int timeLimit);

void printPV(Board b, int limit);

#endif

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