public TranspositionTableEntry(TranspositionTableEntry copy)
{
if (null == copy)
{
return;
}
this.Value = copy.Value;
this.Lock = copy.Lock;
}
public void Store(ulong hashKey, Move m, int depth, int score, TranspositionTableEntry.EntryType type)
{
Stores++;
var index = HashFunction(hashKey);
var existing = TTable[index];
var newEntry = new TranspositionTableEntry {
Type = (byte)type,
Score = (Int16)score,
Depth = depth,
Age = SearchId
};
if (m != null)
{
newEntry.MoveValue = m.Value;
}
newEntry.Lock = newEntry.Value ^ hashKey;
//we will always store the entry in the second bucket
TTable[index + 1] = new TranspositionTableEntry(newEntry);
//check that a result is already present at this index, and decide if we should replace
//if it matches the current position, go ahead and overwrite. If the
//existing entry had been useful, we would not be here.
//this block decides to keep the existing entry
if (existing != null && existing.Lock != newEntry.Lock)
{
// replacement strategy is as follows:
// prefer deeper results
// but we can't keep results around forever just because they are deep
// so we will remember the search (by age) and replace old data first
if (existing.Age == newEntry.Age)
{
if (existing.Depth > depth)
{
return; //the entry that's already here is better and new
}
}
}
TTable[index] = newEntry;
}
int OrderMove(Move m, TranspositionTableEntry entry)
{
if (entry != null)
{
if (m.Value == entry.MoveValue)
{
return(int.MaxValue);// search this move first
}
}
if ((m.Bits & (byte)MoveBits.Capture) > 0)
{
//winning and even captures
if (Evaluator.PieceValueOnSquare(MyBoard, m.To) >= Evaluator.PieceValues[(int)Move.GetPiece((MoveBits)m.Bits)])
{
return(LvaMvv(m));
}
else
{
//verify that it is actually losing with SEE
if (StaticExchange.Eval(MyBoard, m, MyBoard.SideToMove) >= 0)
{
return(LvaMvv(m));
}
return(int.MinValue + LvaMvv(m));//losing captures at the bottom
}
}
else
{
//these happen before losing captures
if (Killers[Ply, 0] != null && Killers[Ply, 0].Value == m.Value)
{
return(2);
}
else if (Killers[Ply, 1] != null && Killers[Ply, 1].Value == m.Value)
{
return(1);
}
}
return(0);
}
void SearchFailHigh(Move m, int score, int depth, TranspositionTableEntry entry)
{
UpdateKillers(m, depth);
Metrics.FailHigh++;
if (entry != null && entry.MoveValue == m.Value)
{
Metrics.TTFailHigh++;
}
else if ((Killers[Ply, 0] != null && m.Value == Killers[Ply, 0].Value) ||
(Killers[Ply, 1] != null && m.Value == Killers[Ply, 1].Value))
{
Metrics.KillerFailHigh++;
}
//update the transposition table
//the move doesn't matter if it is a CUT node
TranspositionTable.Instance.Store(
MyBoard.HashKey, m, depth, score, TranspositionTableEntry.EntryType.CUT);
}