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6a8e46d)
If we want to store a value of type VALUE_TYPE_EVAL for
a given position and we found an already exsisting entry
for the same position then we skip.
We don't want to overwrite a more valuable score with a
lesser one. Note that also in case the exsisting entry is
of VALUE_TYPE_EVAL type the overwrite is unuseful because
we would store the same score again.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
/// the least valuable of the four entries in a cluster. A TTEntry t1 is
/// considered to be 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
/// the least valuable of the four entries in a cluster. A TTEntry t1 is
/// considered to be 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.
+/// 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,
Move m, ValueType type) {
TTEntry* TranspositionTable::store(const Position &pos, Value v, Depth d,
Move m, ValueType type) {
{
if (!tte->key() || tte->key() == pos.get_key()) // empty or overwrite old
{
{
if (!tte->key() || tte->key() == pos.get_key()) // empty or overwrite old
{
+ // Do not overwrite position entry when VALUE_TYPE_EVAL
+ if ( tte->key()
+ && type == VALUE_TYPE_EVAL)
+ return NULL;
+
if (m == MOVE_NONE)
m = tte->move();
if (m == MOVE_NONE)
m = tte->move();