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Allow negative history values

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Don't clamp to zero if a move continues to fail.

After 946 games at 1+0
Mod vs Orig +208 =562 -176 +12 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2010-01-12 18:21:15 +01:00
parent 007285be2d
commit 942c18ef66
1 changed files with 6 additions and 2 deletions
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8
src/history.cpp
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@@ -75,8 +75,12 @@ void History::failure(Piece p, Square to, Depth d) {
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;
}