After history accounting rewrite in 1.6, a small
tweak of history parameters seems positive.
Note that these are not to be considered the optimal
values, just a wild guess that proved good.
Finding the optimal values would require a much longer
testing time.
After 967 games at 1+0
Mod vs Orig 240 529 198 +15 ELO
Functionality Signature:
21222553
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
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;
}
/// 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 4. It is difficult to guess what
+/// 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.
-const int HistoryMax = 25000 * OnePly;
+const int HistoryMax = 50000 * OnePly;
#endif // !defined(HISTORY_H_INCLUDED)