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Double HistoryMax and reduce aging

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>
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1 parent 0f39e5c commit 78246035499e277a7099b73bb96ac1e115643d61 @mcostalba committed Dec 31, 2009
Showing with 3 additions and 3 deletions.
  1. +1 −1 src/history.cpp
  2. +2 −2 src/history.h
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@@ -61,7 +61,7 @@ void History::success(Piece p, Square to, Depth d) {
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;
}
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@@ -61,13 +61,13 @@ class History {
/// 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)

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