/// <summary>
/// Probes the transposition table for a entry that matches the position key.
/// </summary>
/// <param name="key">The position key</param>
/// <returns>(true, entry) if one was found, (false, empty) if not found</returns>
public (bool, TranspositionTableEntry) Probe(ulong key)
{
var ttc = FindCluster(key);
var keyH = (uint)(key >> 32);
var g = _generation;
// Probing the Table will automatically update the generation of the entry
// in case the probing retrieves an element.
TranspositionTableEntry e = default;
var set = false;
for (var i = 0; i < ttc.Cluster.Length; ++i)
{
if (ttc.Cluster[i].Key32 != 0 && ttc.Cluster[i].Key32 != keyH)
{
continue;
}
ttc.Cluster[i].Generation = g;
e = ttc.Cluster[i];
set = true;
break;
}
if (set)
{
Hits++;
}
return(set, e);
}
public void Save(TranspositionTableEntry tte)
{
Key32 = tte.Key32;
if (tte.Move != MoveExtensions.EmptyMove)
{
Move = tte.Move;
}
Depth = tte.Depth;
Generation = tte.Generation;
Value = tte.Value;
StaticValue = tte.StaticValue;
Type = tte.Type;
}
/// <summary>
/// Stores a move in the transposition table.
/// It will automatically detect the best cluster location to store it in.
/// If a similar move already is present, a simple check if done to make sure
/// it actually is an improvement of the previous move.
/// </summary>
/// <param name="key">The position key</param>
/// <param name="value">The value of the move</param>
/// <param name="type">The bound type, e.i. did it exceed alpha or beta</param>
/// <param name="depth">The depth of the move</param>
/// <param name="move">The move it self</param>
/// <param name="statValue">The static value of the move</param>
public void Store(ulong key, int value, Bound type, sbyte depth, Move move, int statValue)
{
// Use the high 32 bits as key inside the cluster
var e = new TranspositionTableEntry((uint)(key >> 32), move, depth, _generation, value, statValue, type);
var ttc = FindCluster(key);
var clusterIndex = 0;
var found = false;
for (var i = 0; i < ttc.Cluster.Length; ++i)
{
if (ttc.Cluster[i].Key32 == 0 || ttc.Cluster[i].Key32 == e.Key32)
{
clusterIndex = i;
found = true;
break;
}
}
if (!found)
{
var index = 0;
var candidate = ttc.Cluster[index];
var g = _generation;
for (var i = 0; i < ttc.Cluster.Length; ++i)
{
var ttEntry = ttc.Cluster[i];
var(cc1, cc2, cc3, cc4) =
(candidate.Generation == g,
ttEntry.Generation == g,
ttEntry.Type == Bound.Exact,
ttEntry.Depth < candidate.Depth);
if (cc1 && cc4 || !(cc2 || cc3) && (cc4 || cc1))
{
index = i;
candidate = ttEntry;
}
}
clusterIndex = index;
}
ttc.Cluster[clusterIndex].Save(e);
}
public void Refresh(TranspositionTableEntry tte) => tte.Generation = _generation;
public TTCluster()
{
Cluster = new TranspositionTableEntry[4];
Array.Copy(Defaults, Cluster, Defaults.Length);
}
public TranspositionTableEntry(TranspositionTableEntry tte)
{
this = tte;
}