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Revert setting a flag when TT value equals static evaluation

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Strangely enough it seems that optimization doesn't work.

After 760 games at 1+0: +155 -184 =421 -13 ELO

Probably the overhead, although small, for setting the flag
is not compensated by the saved evaluation call.

This could be due to the fact that after a TT value is stored,
if and when we hit the position again the stored TT value is
actually used as a cut-off so that we don't need to go on
with another search and evaluation is avoided in any case.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-03-31 14:57:44 +02:00
parent 2c0cd95ecf
commit 659c54582d
3 changed files with 8 additions and 23 deletions
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17
src/search.cpp
View file

@ -1455,7 +1455,7 @@ namespace {
if (isCheck)
staticValue = -VALUE_INFINITE;
else if (tte && (tte->type() == VALUE_TYPE_EVAL || tte->staticValue()))
else if (tte && tte->type() == VALUE_TYPE_EVAL)
{
// Use the cached evaluation score if possible
assert(tte->value() == evaluate(pos, ei, threadID));
@ -1569,21 +1569,10 @@ namespace {
if (!pvNode)
{
Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
Value v = value_to_tt(bestValue, ply);
TTEntry* e;
if (bestValue < beta)
e = TT.store(pos, v, d, MOVE_NONE, VALUE_TYPE_UPPER);
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER);
else
e = TT.store(pos, v, d, MOVE_NONE, VALUE_TYPE_LOWER);
assert(e && e == TT.retrieve(pos));
assert(!e->staticValue());
// If the just stored value happens to be equal to the static evaluation
// score then set the flag, so to avoid calling evaluation() next time we
// hit this position.
if (staticValue == v && !ei.futilityMargin)
e->setStaticValue();
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_LOWER);
}
// Update killers only for good check moves

7
src/tt.cpp
View file

@ -104,7 +104,7 @@ void TranspositionTable::clear() {
/// is bigger than the depth of t2. A TTEntry of type VALUE_TYPE_EVAL
/// never replaces another entry for the same position.
TTEntry* TranspositionTable::store(const Position &pos, Value v, Depth d,
void TranspositionTable::store(const Position &pos, Value v, Depth d,
Move m, ValueType type) {
TTEntry *tte, *replace;
@ -116,13 +116,13 @@ TTEntry* TranspositionTable::store(const Position &pos, Value v, Depth d,
// Do not overwrite position entry when VALUE_TYPE_EVAL
if ( tte->key()
&& type == VALUE_TYPE_EVAL)
return NULL;
return;
if (m == MOVE_NONE)
m = tte->move();
*tte = TTEntry(pos.get_key(), v, type, d, m, generation);
return tte;
return;
}
else if (i == 0) // replace would be a no-op in this common case
continue;
@ -136,7 +136,6 @@ TTEntry* TranspositionTable::store(const Position &pos, Value v, Depth d,
}
*replace = TTEntry(pos.get_key(), v, type, d, m, generation);
writes++;
return replace;
}

7
src/tt.h
View file

@ -46,8 +46,7 @@
/// the 32 bits of the data field are so defined
///
/// bit 0-16: move
/// bit 17: stored value equals static value
/// bit 18-19: not used
/// bit 17-19: not used
/// bit 20-22: value type
/// bit 23-31: generation
@ -62,8 +61,6 @@ public:
Value value() const { return Value(value_); }
ValueType type() const { return ValueType((data >> 20) & 7); }
int generation() const { return (data >> 23); }
bool staticValue() const { return ((data >> 17) & 1); }
void setStaticValue() { data |= (1 << 17); }
private:
Key key_;
@ -83,7 +80,7 @@ public:
~TranspositionTable();
void set_size(unsigned mbSize);
void clear();
TTEntry* store(const Position &pos, Value v, Depth d, Move m, ValueType type);
void store(const Position &pos, Value v, Depth d, Move m, ValueType type);
TTEntry* retrieve(const Position &pos) const;
void new_search();
void insert_pv(const Position &pos, Move pv[]);