SimpleSelect.cpp

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#include "SimpleSelect.h"
#include <cmath>
#include <iostream>
using namespace std;
SimpleSelect::SimpleSelect(GeneralRNG &LocalRandom, tProbabilityFunction myPF):
Random(LocalRandom),
ProbabilityFunction(myPF)
{
        
}

SimpleSelect::~SimpleSelect()
{}

void SimpleSelect::DoInit()
{
        const tprobabilityv probabilities = ProbabilityFunction();
        const int popsize = probabilities.size();
        int currentindex = 0;
        double expsum = 0;
        int assignsum = 0;

        std::vector<double> fraction(popsize,0);
        indices.assign(popsize,0);
        
        cout << "Probs: ";
        for (int i= 0; i < popsize; ++i)
                cout << probabilities(i) << " ";
        cout << endl;
        
    remain = popsize;
    //cout << "Expected: ";
    
    for (int i = 0; i < popsize; ++i)
    {
                double expected = probabilities(i) * popsize;
                //cout << expected << " ";
                expsum += expected;
                int assign = int(floor(expected));
                assignsum += assign;
                fraction.at(i) = expected -assign;
                while (assign > 0)
                {
                --assign;
                indices.at(currentindex) = i;
                ++currentindex;
                }
        
    }
    /*cout << endl;
    cout << "Expsum: " << expsum << " Assignsum: " << assignsum << endl; 
    cout << "Fractions: " << endl << flush;*/
    int fractionindex = 0;
    while (currentindex < popsize)
    {
                if (  Random.GetNumber() <= fraction.at(fractionindex) )
            {
                //cout << "f: " << fraction.at(fractionindex) << " i:" << currentindex << endl;
                        indices.at(currentindex)=fractionindex;
                        ++currentindex;
                        fraction.at(fractionindex) -= 1.0;
            }
                ++fractionindex;
                if (fractionindex >= popsize)
                fractionindex -= popsize;
    }
   //cout << endl;
}

size_t SimpleSelect::DoGetOne()
{
    int pick = Random.GetNumber(remain);
    int result = indices.at(pick);
    --remain; // Have to reduce remain before because it starts with popsize but array is 0..popsize-1
    indices.at(pick) = indices.at(remain);
    return(result);
}

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