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Retire eval margin and gains

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1/ eval margin and gains removed:
 - gains removed by Value(128): search() and qsearch() now behave consistently!

2/ futility_margin()
 - testing showed that there is no added value in this weird (log(depth), movecount)
   formula, and a much simpler linear formula is just as good. In fact, it is most
   likely better, as it is not yet optimally tuned.
 - the new simplified formula also means we get rid of FutilityMargins[], its
   initialization code, and more importantly ss->futilityMoveCount, and the hacky
   code that updates it throughout the search().
 - the current formula gives negative futility margins, and there is a hidden interaction
   between the move coutn pruning formula and the futility margin one: what happens is
   that MCP is supposed to be triggered before we use the non-sensical negative futility
   margins.

3/ unify pre & post futility pruning
 - pre futility pruning (what SF calls value based pruning) used depth < 7 plies,
   while post futility pruning (what SF calls static null move pruning) used depth < 4 plies.
 - also the condition depth < 7 in pre futility pruning was not obvious, and it seemd
   to be depth < 16 (futility_margin() returns an infinite value when depth >= 7).

Tested with fixed number of games both at short TC:
ELO: 0.82 +-2.1 (95%) LOS: 77.3%
Total: 40000 W: 7939 L: 7845 D: 24216

And long TC
ELO: 0.59 +-2.0 (95%) LOS: 71.9%
Total: 40000 W: 6876 L: 6808 D: 26316

bench: 10206576
This commit is contained in:
Lucas Braesch
2013-10-30 11:22:42 +08:00
committed by Marco Costalba
parent 52ae0efccf
commit ecd07e51d0
7 changed files with 47 additions and 112 deletions
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4
src/tt.cpp
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@@ -89,7 +89,7 @@ const TTEntry* TranspositionTable::probe(const Key key) const {
/// more valuable than a TTEntry t2 if t1 is from the current search and t2 is from
/// a previous search, or if the depth of t1 is bigger than the depth of t2.
void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV, Value evalM) {
void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m, Value statV) {
int c1, c2, c3;
TTEntry *tte, *replace;
@@ -117,5 +117,5 @@ void TranspositionTable::store(const Key key, Value v, Bound b, Depth d, Move m,
replace = tte;
}
replace->save(key32, v, b, d, m, generation, statV, evalM);
replace->save(key32, v, b, d, m, generation, statV);
}