/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2009 Marco Costalba
+ Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
/// History::clear() clears the history tables
void History::clear() {
- memset(history, 0, 2 * 8 * 64 * sizeof(int));
+ memset(history, 0, 16 * 64 * sizeof(int));
+ memset(maxStaticValueDelta, 0, 16 * 64 * sizeof(int));
}
if (history[p][to] >= HistoryMax)
for (int i = 0; i < 16; i++)
for (int j = 0; j < 64; j++)
- history[i][j] /= 4;
+ history[i][j] /= 2;
}
assert(square_is_ok(to));
history[p][to] -= int(d) * int(d);
- if (history[p][to] < 0)
- history[p][to] = 0;
-}
+ // Prevent history underflow
+ if (history[p][to] <= -HistoryMax)
+ for (int i = 0; i < 16; i++)
+ for (int j = 0; j < 64; j++)
+ history[i][j] /= 2;
+}
-/// 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, Square to) const {
+/// History::set_gain() and History::gain() store and retrieve the
+/// gain of a move given the delta of the static position evaluations
+/// before and after the move.
- assert(piece_is_ok(p));
- assert(square_is_ok(to));
+void History::set_gain(Piece p, Square to, Value delta) {
- return history[p][to];
+ if (delta >= maxStaticValueDelta[p][to])
+ maxStaticValueDelta[p][to] = delta;
+ else
+ maxStaticValueDelta[p][to]--;
}