// get the node ids in 1-connected components
void Get1CnCom(const PUNGraph& Graph, TCnComV& Cn1ComV) {
//TCnCom::GetWccCnt(Graph, SzCntV); IAssertR(SzCntV.Len() == 1, "Graph is not connected.");
TIntPrV EdgeV;
GetEdgeBridges(Graph, EdgeV);
if (EdgeV.Empty()) { Cn1ComV.Clr(false); return; }
PUNGraph TmpG = TUNGraph::New();
*TmpG = *Graph;
for (int e = 0; e < EdgeV.Len(); e++) {
TmpG->DelEdge(EdgeV[e].Val1, EdgeV[e].Val2); }
TCnComV CnComV; GetWccs(TmpG, CnComV);
IAssert(CnComV.Len() >= 2);
const TIntV& MxWcc = CnComV[0].NIdV;
TIntSet MxCcSet(MxWcc.Len());
for (int i = 0; i < MxWcc.Len(); i++) {
MxCcSet.AddKey(MxWcc[i]); }
// create new graph: bridges not touching MxCc of G with no bridges
for (int e = 0; e < EdgeV.Len(); e++) {
if (! MxCcSet.IsKey(EdgeV[e].Val1) && ! MxCcSet.IsKey(EdgeV[e].Val2)) {
TmpG->AddEdge(EdgeV[e].Val1, EdgeV[e].Val2); }
}
GetWccs(TmpG, Cn1ComV);
// remove the largest component of G
for (int c = 0; c < Cn1ComV.Len(); c++) {
if (MxCcSet.IsKey(Cn1ComV[c].NIdV[0])) {
Cn1ComV.Del(c); break; }
}
}
// Maximum modularity clustering by Girvan-Newman algorithm (slow)
// Girvan M. and Newman M. E. J., Community structure in social and biological networks, Proc. Natl. Acad. Sci. USA 99, 7821–7826 (2002)
double CommunityGirvanNewman(PUNGraph& Graph, TCnComV& CmtyV) {
TIntH OutDegH;
const int NEdges = Graph->GetEdges();
for (TUNGraph::TNodeI NI = Graph->BegNI(); NI < Graph->EndNI(); NI++) {
OutDegH.AddDat(NI.GetId(), NI.GetOutDeg());
}
double BestQ = -1; // modularity
TCnComV CurCmtyV;
CmtyV.Clr();
TIntV Cmty1, Cmty2;
while (true) {
CmtyGirvanNewmanStep(Graph, Cmty1, Cmty2);
const double Q = _GirvanNewmanGetModularity(Graph, OutDegH, NEdges, CurCmtyV);
//printf("current modularity: %f\n", Q);
if (Q > BestQ) {
BestQ = Q;
CmtyV.Swap(CurCmtyV);
}
if (Cmty1.Len()==0 || Cmty2.Len() == 0) { break; }
}
return BestQ;
}
