NxReal DrawFromBoundedPowerLaw( float a0, float a1, float alfa )
{
// using the inverse transformation law for probabilities. see for example, NR3 p.362, although the explanation sucks.
// for the pdf p(a)=C*a^-alfa, between a0 and a1.
float t=gRNG.doub();
float onemalfa=1-alfa;
float a = NxMath::pow(t*(NxMath::pow(a1,onemalfa)-NxMath::pow(a0,onemalfa)) + NxMath::pow(a0,onemalfa) , 1.0f/(onemalfa));
return a;
}
/*
Utility method to boot-strap the current node set size.
Randomly select 80% of nodes from current node set.
*/
void getSubSample( vector<int> &keys ) {
vector<node> Cn;
vector<edge> Celist;
for(int i=1; i<Gn.size(); i++) {
Gn[i].c = -1;
Cn.push_back(Gn[i].Clone());
}
for(int i=0; i<Gelist.size(); i++) {
Celist.push_back(Gelist[i].Clone());
}
vector<int> rmKeys;
vector<int> rmEdgeKeys;
int N = Cn.size();
int sample_size = 0;
double subN = 0.8; //set to sample 80% of the current node set size.
//generate a sub-sample using bootstrapped method
while( sample_size < N*subN ) {
int rnd_ind = (int)floor( _rand.doub() * (N+1) );
if(Cn[rnd_ind].c == -1) {
Cn[rnd_ind].c = 1;
sample_size++;
}
}
for(int i=0; i<Cn.size(); i++) {
if(Cn[i].c == -1) {
keys[i] = -1;
rmKeys.push_back(Cn[i].k);
}
}
for(int i=0; i<rmKeys.size(); i++) {
for(int k=0; k<Celist.size(); k++) {
if( Celist[k].so == rmKeys[i]) {
Celist[k].so = -1;
Celist[k].si = -1;
}
}
for(int k=0; k<Celist.size(); k++) {
if( Celist[k].si == rmKeys[i]) {
Celist[k].so = -1;
Celist[k].si = -1;
}
}
}
reader.enumerateNodeList(Cn, Celist, n, elist);
Cn.swap(emptyn);
Celist.swap(emptye);
}
