// /**
// * Clear objects cached for efficiency when the
// * object state changes.
// *
// * Messy since state can be changed outside
// * but helps with runtimes.
// */
// public void clearCachedObjects(){
// graphHash = null;
//// hashCode = 0;
// groundGraphHash = null;
// }
//
/**
* Produces a cheap copy of the graph, where immutable objects
* (graph structure, static hashes, hash function) are copied by pointer,
* whereas dynamic objects (dynamic hashes) are shallow-copied
* @return
*/
public HashGraph Branch()
{
Dictionary <Node, string> dh = new Dictionary <Node, string>(_dynamicHashes);
HashGraph hg = new HashGraph(_hf, _data, _staticHashes, _blankHash, dh);
return(hg);
}
/**
* Hash all blank nodes with the mux
* @param mux
* @return
*/
public static void MuxHash(HashGraph hg, string mux)
{
HashSet <Node> bnodes = new HashSet <Node>(hg.GetBlankNodeHashes().Keys);
foreach (var b in bnodes)
{
string hc = hg.GetHash(b);
var tup = new string[] { hc, mux };
string comb = _hf.CombineOrdered(tup);
hg.GetBlankNodeHashes().Add(b, comb);
}
}
/**
* Splits the hashgraph into multiple where each
* graph represents all triples for each set of connected blank nodes
* (blank nodes appearing in the same triple).
*
* Ground triples are removed (if previously present).
*
* Shallow copy: colours are preserved.
*
* @return
*/
public ICollection <HashGraph> BlankNodePartition()
{
var part = new Partition <Node>();
// first create a partition of blank nodes based
// on being connected
foreach (Triple t in _data)
{
if (t.Subject.IsBlankNode() && t.Object.IsBlankNode() && !t.Subject.Equals(t.Object))
{
part.AddPair(t.Subject as Node, t.Object as Node);
}
}
var pivotToGraph = new Dictionary <Node, HashGraph>();
foreach (var t in _data)
{
// doesn't matter which we pick, both are in the
// same partition
BlankNode b = null;
if (t.Subject.IsBlankNode())
{
b = t.Subject.AsBlankNode();
}
else if (t.Object.IsBlankNode())
{
b = t.Object.AsBlankNode();
}
else
{
continue;
}
// use the lowest bnode in the partition
// to map to its graph
var bp = part.GetPartition(b);
Node pivot = null;
if (bp == null || bp.Count == 0)
{
pivot = b; // singleton ... unconnected blank node
}
else
{
pivot = bp[0];
}
HashGraph hg;
if (!pivotToGraph.ContainsKey(pivot))
{
hg = new HashGraph(_hf);
pivotToGraph.Add(pivot, hg);
}
else
{
hg = pivotToGraph[pivot];
}
hg.AddTriple(t);
}
return(pivotToGraph.Values);
}