RatioBasedSpliter.cpp

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#include "RatioBasedSpliter.h"
#include "PCSIMException.h"
#include "Point3DSet.h"
#include <boost/format.hpp>

UniformDistribution RatioBasedSpliter::prob_zero_one(0,1);

RatioBasedSpliter::RatioBasedSpliter( vector<double> const& ratios )
        : Point3DSetSpliter() {

    if( ratios.size() < 1 ) {
        throw( PCSIM::ConstructionException( "RatioBasedFamilies::RatioBasedFamilies", str( boost::format("Empty sequence of ratios not allowed") ) ) );
    }
    probabilities.resize( ratios.size() );
    cumsum.resize( ratios.size() );
    double sum = 0.0;
    size_t i;
    for( i=0; i<ratios.size(); i++ ) {
        sum += fabs( ratios[i] );
    }
    for( i=0; i<ratios.size(); i++ ) {
        probabilities[i] = fabs( ratios[i] ) / sum;
    }
    cumsum[0] = probabilities[0];
    for( i=1; i<ratios.size(); i++ ) {
        cumsum[i] = cumsum[i-1] +  probabilities[i];
    }
}

shared_ptr< vector< shared_ptr<Point3DSet> > > RatioBasedSpliter::split( Point3DSet const& points ) {

    
    shared_ptr< vector< shared_ptr<Point3DSet> > > parts( new vector< shared_ptr<Point3DSet> >( cumsum.size() ) );

    for( size_t s = 0; s < parts->size(); s++ ) {
        (*parts)[s] = shared_ptr<Point3DSet>( new Point3DSet( 0 ) );
    }


    double p;
    int s;
    for( size_t i=0; i<points.size(); i++ ) {
        p = prob_zero_one.get( *m_rnd_eng );
        // For large number of rations a binary search might be faster here. But for low numbers ...
        for( s=0; cumsum[s]<p; s++);
        (*parts)[s]->append( points[i] );
    }

    return parts;

}

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