//// Functions
////
+
/// Constructor
-History::History() {
- this->clear();
-}
+History::History() { clear(); }
-/// History::clear() clears the history tables.
+/// History::clear() clears the history tables
void History::clear() {
memset(history, 0, 2 * 8 * 64 * sizeof(int));
}
-/// History::success() registers a move as being successful. This is done
+/// History::success() registers a move as being successful. This is done
/// whenever a non-capturing move causes a beta cutoff in the main search.
-/// The three parameters are the moving piece, the move itself, and the
-/// search depth.
+/// The three parameters are the moving piece, the destination square, and
+/// the search depth.
+
+void History::success(Piece p, Square to, Depth d) {
-void History::success(Piece p, Move m, Depth d) {
assert(piece_is_ok(p));
- assert(move_is_ok(m));
+ assert(square_is_ok(to));
- history[p][move_to(m)] += int(d) * int(d);
- successCount[p][move_to(m)]++;
+ history[p][to] += int(d) * int(d);
+ successCount[p][to]++;
- // Prevent history overflow:
- if(history[p][move_to(m)] >= HistoryMax)
- for(int i = 0; i < 16; i++)
- for(int j = 0; j < 64; j++)
- history[i][j] /= 2;
+ // Prevent history overflow
+ if (history[p][to] >= HistoryMax)
+ for (int i = 0; i < 16; i++)
+ for (int j = 0; j < 64; j++)
+ history[i][j] /= 2;
}
-/// History::failure() registers a move as being unsuccessful. The function is
+/// History::failure() registers a move as being unsuccessful. The function is
/// called for each non-capturing move which failed to produce a beta cutoff
/// at a node where a beta cutoff was finally found.
-void History::failure(Piece p, Move m) {
+void History::failure(Piece p, Square to) {
+
assert(piece_is_ok(p));
- assert(move_is_ok(m));
+ assert(square_is_ok(to));
- failureCount[p][move_to(m)]++;
+ failureCount[p][to]++;
}
/// History::move_ordering_score() returns an integer value used to order the
/// non-capturing moves in the MovePicker class.
-int History::move_ordering_score(Piece p, Move m) const {
+int History::move_ordering_score(Piece p, Square to) const {
+
assert(piece_is_ok(p));
- assert(move_is_ok(m));
+ assert(square_is_ok(to));
- return history[p][move_to(m)];
+ return history[p][to];
}
/// History::ok_to_prune() decides whether a move has been sufficiently
/// unsuccessful that it makes sense to prune it entirely.
-bool History::ok_to_prune(Piece p, Move m, Depth d) const {
+bool History::ok_to_prune(Piece p, Square to, Depth d) const {
+
assert(piece_is_ok(p));
- assert(move_is_ok(m));
+ assert(square_is_ok(to));
- return (int(d) * successCount[p][move_to(m)] < failureCount[p][move_to(m)]);
+ return (int(d) * successCount[p][to] < failureCount[p][to]);
}
//// Types
////
-/// The History class stores statistics about how often different moves have
-/// been successful or unsuccessful during the current search. These
-/// statistics are used for reduction and move ordering decisions.
+/// The History class stores statistics about how often different moves
+/// have been successful or unsuccessful during the current search. These
+/// statistics are used for reduction and move ordering decisions. History
+/// entries are stored according only to moving piece and destination square,
+/// in particular two moves with different origin but same destination and
+/// same piece will be considered identical.
class History {
public:
History();
void clear();
- void success(Piece p, Move m, Depth d);
- void failure(Piece p, Move m);
- int move_ordering_score(Piece p, Move m) const;
- bool ok_to_prune(Piece p, Move m, Depth d) const;
+ void success(Piece p, Square to, Depth d);
+ void failure(Piece p, Square to);
+ int move_ordering_score(Piece p, Square to) const;
+ bool ok_to_prune(Piece p, Square to, Depth d) const;
private:
int history[16][64]; // [piece][square]
/// HistoryMax controls how often the history counters will be scaled down:
/// When the history score for a move gets bigger than HistoryMax, all
-/// entries in the table are divided by 2. It is difficult to guess what
-/// the ideal value of this constant is. Scaling down the scores often has
+/// entries in the table are divided by 2. It is difficult to guess what
+/// the ideal value of this constant is. Scaling down the scores often has
/// the effect that parts of the search tree which have been searched
/// recently have a bigger importance for move ordering than the moves which
/// have been searched a long time ago.
///
/// Note that HistoryMax should probably be changed whenever the constant
-/// OnePly in depth.h is changed. This is somewhat annoying. Perhaps it
+/// OnePly in depth.h is changed. This is somewhat annoying. Perhaps it
/// would be better to scale down the history table at regular intervals?
const int HistoryMax = 50000;
else if (m == killer2)
hs = HistoryMax + 1;
else
- hs = H.move_ordering_score(pos.piece_on(move_from(m)), m);
+ hs = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
// Ensure history is always preferred to pst
if (hs > 0)
int seeScore = pos.see(m);
moves[i].score = (seeScore >= 0)? seeScore + HistoryMax : seeScore;
} else
- moves[i].score = H.move_ordering_score(pos.piece_on(move_from(m)), m);
+ moves[i].score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
}
}
return false;
// Case 4: Don't prune moves with good history.
- if (!H.ok_to_prune(pos.piece_on(move_from(m)), m, d))
+ if (!H.ok_to_prune(pos.piece_on(mfrom), mto, d))
return false;
// Case 5: If the moving piece in the threatened move is a slider, don't
void update_history(const Position& pos, Move m, Depth depth,
Move movesSearched[], int moveCount) {
- H.success(pos.piece_on(move_from(m)), m, depth);
+ H.success(pos.piece_on(move_from(m)), move_to(m), depth);
for (int i = 0; i < moveCount - 1; i++)
{
assert(m != movesSearched[i]);
if (ok_to_history(pos, movesSearched[i]))
- H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]);
+ H.failure(pos.piece_on(move_from(movesSearched[i])), move_to(movesSearched[i]));
}
}