Trip Based Gravity Restructure.cpp

// SETUP CODE
// ALPHA < 0, BETA > 0?
bool has_min_deterrence = (alpha < 0 && beta > 0);
float turn_cost, min_utility = 0.0;
if (has_min_deterrence)
{
    turn_cost   = -alpha / beta;
    min_utility = beta * turn_cost + alpha * log(turn_cost);
}

for (int i = 0; i < numCentroids; ++i)
{
    if (attractions.at(i) > 0) log_attractions.at(i) = log(attractions.at(i));
        
    float* skim_row        = skim.Lock(i);
    float* adj_skim_row = adj_skim.Lock(i);
    float* log_skim_row = log_skim.Lock(i);

    for (int j = 0; j < numCentroids; ++j)
    {
        float skim_value = has_min_deterrence ? std::min(skim_row[j], turn_cost) : skim_row[j];
        if (skim_value < 0.0) 
        {
            string str = "skim value was <= 0 at (" + ToString(i) + "," + ToString(j) + ")";
            otRuby->rb_raise(otRuby->rb_eRuntimeError(), str.c_str());
        }
            
        adj_skim_row[j] = skim_value * destination_cost_factors.at(j) + destination_constants.at(j);
        log_skim_row[j] = log(skim_value);
    }
}
// Then main loop was this:
for (int col = 0; col < numCentroids; ++col)
{
    float skim_value = skim_row[col];
			
    if (attractions.at(col) == 0 || skim_value == 99999)
    {
        utilities.at(col) = 99999;
        continue;
    }

    float adj_skim_value = adj_skim_row[col];
    float log_skim_value = log_skim_row[col];
            
    if (has_min_deterrence)
    {
        if (skim_value >= turn_cost)
            utilities.at(col) = 99999.0;
        else
        {
            float cost_based_utility = alpha * log_skim_value + beta * adj_skim_value - min_utility;

            if (cost_based_utility < 0)
                utilities.at(col) = 99999;
            else
            {
                utilities.at(col) = log_attractions.at(col) + cost_based_utility;
            }
        }
    }
    else
    {
        utilities.at(col) = log_attractions.at(col) + alpha * log_skim_value + beta * adj_skim_value;
    }
            
    if (utilities.at(col) != 99999 && utilities.at(col) > maxV)
    {
        maxV = utilities.at(col);
        destinationWithMaxV = col;
    }
}


// Becomes, this:
for (int col = 0; col < numCentroids; ++col)
{
    float skim_value = skim_row[col];
			
    if (attractions.at(col) == 0 || skim_value == 99999)
    {
        utilities.at(col) = 99999;
        continue;
    }

    float cost_based_utility = alpha * log_skim_row[col] + beta * adj_skim_row[col] - min_utility;
    utilities.at(col) = (cost_based_utility < 0) ? 99999 : log_attractions.at(col) + cost_based_utility;
            
    if (utilities.at(col) != 99999 && utilities.at(col) > maxV)
    {
        maxV = utilities.at(col);
        destinationWithMaxV = col;
    }
}