RandomConnections.cpp

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#include "RandomConnections.h"

RandomConnections::RandomConnections( const double conn_prob ) :
        conn_prob(conn_prob)
{
    if (conn_prob <= 0 || conn_prob > 1)
        throw PCSIM::Exception( "RandomConnections::RandomConnections" , "Connection probability must lie in interval (0,1]" );
    if (conn_prob != 1)
        geom_rnd = new GeometricDistribution(1 - conn_prob);
}


RandomConnections::RandomConnections( const double conn_prob, MPI::Intracomm const& ) :
        conn_prob(conn_prob)
{
    if (conn_prob <= 0 || conn_prob > 1)
        throw PCSIM::Exception( "RandomConnections::RandomConnections" , "Connection probability must lie in interval (0,1]" );
    if (conn_prob != 1)
        geom_rnd = new GeometricDistribution(1 - conn_prob );
}


RandomConnections::~RandomConnections()
{
    if (conn_prob != 1)
        delete geom_rnd;
}

void RandomConnections::init(const SimObjectPopulation &srcPopulation, const SimObjectPopulation &destPopulation)
{
    /* NOOP - populations not needed for pure random connections */
    src_popul =  &srcPopulation;
    dest_popul = &destPopulation;
}

size_t RandomConnections::estimate()
{
    return 0;
}

void RandomConnections::reset(SimObject::ID::SortedVector::const_iterator src_begin_it,
        SimObject::ID::SortedVector::const_iterator src_end_it,
        SimObject::ID::SortedVector::const_iterator dest_begin_it,
        SimObject::ID::SortedVector::const_iterator dest_end_it)
{
    curr_src_idx = 0;
    curr_dest_idx = -1;

    //------
    from_begin_it = src_begin_it;
    to_begin_it = dest_begin_it;
    src_max_idx = src_end_it - src_begin_it;
    dest_max_idx = dest_end_it - dest_begin_it;
}

bool RandomConnections:: next( pair<SimObject::ID, SimObject::ID> &conn_pair )
{
    last_conn_valid = false;

    size_t step;
    if (conn_prob == 1)
        step = 1;
    else
        step = size_t( (*geom_rnd)( *m_rnd_eng ) );

    // jump random number of steps in the pair set (geometric distribution)
    while (true) {
        curr_dest_idx += step;

        if (curr_dest_idx >= dest_max_idx) {
            curr_src_idx += size_t(curr_dest_idx / dest_max_idx );
            curr_dest_idx %= dest_max_idx;
        }

        if (curr_src_idx < src_max_idx)
        {
            last_conn_idx.first = *(from_begin_it + curr_src_idx);
            conn_pair.first = (*src_popul).getID(last_conn_idx.first);

            last_conn_idx.second = *(to_begin_it + curr_dest_idx);
            conn_pair.second = (*dest_popul).getID(last_conn_idx.second);
        }
        else
            return false;
        // check if connection is self loop
        if (conn_pair.first == conn_pair.second)
            if (conn_prob == 1)
                step = 1;
            else
                step = size_t( (*geom_rnd)( *m_rnd_eng ) ); // we have self-loop so go to the next pair
        else
            break;  // found a good connection
    }

    last_conn_valid = true;

    return true;
}

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