///Generate sequence from Power law
void TAGMUtil::GenPLSeq(TIntV& SzSeq, const int& SeqLen, const double& Alpha, TRnd& Rnd, const int& Min, const int& Max) {
SzSeq.Gen(SeqLen, 0);
while (SzSeq.Len() < SeqLen) {
int Sz = (int) TMath::Round(Rnd.GetPowerDev(Alpha));
if (Sz >= Min && Sz <= Max) {
SzSeq.Add(Sz);
}
}
}
/// Generates a random scale-free graph with power-law degree distribution with
/// exponent PowerExp. The method uses either the Configuration model (fast but
/// the result is approximate) or the Edge Rewiring method (slow but exact).
PUNGraph GenRndPowerLaw(const int& Nodes, const double& PowerExp, const bool& ConfModel, TRnd& Rnd) {
TIntV DegSeqV;
uint DegSum=0;
for (int n = 0; n < Nodes; n++) {
const int Val = (int) TMath::Round(Rnd.GetPowerDev(PowerExp));
if (! (Val >= 1 && Val < Nodes/2)) { n--; continue; } // skip nodes with too large degree
DegSeqV.Add(Val);
DegSum += Val;
}
printf("%d nodes, %u edges\n", Nodes, DegSum);
if (DegSum % 2 == 1) { DegSeqV[0] += 1; }
if (ConfModel) {
// use configuration model -- fast but does not exactly obey the degree sequence
return GenConfModel(DegSeqV, Rnd);
} else {
PUNGraph G = TSnap::GenDegSeq(DegSeqV, Rnd);
return TSnap::GenRewire(G, 10, Rnd);
}
}