/// <summary>
/// Pick an array element with probability proportional to exp(-cost).
/// </summary>
public static int sample_by_costs(Floatarray costs)
{
Doublearray p = new Doublearray();
p.Copy(costs);
double mincost = NarrayUtil.Min(costs);
p -= mincost;
for (int i = 0; i < p.Length(); i++)
{
p.UnsafePut1d(i, Math.Exp(-p.UnsafeAt1d(i)));
}
double sump = NarrayUtil.Sum(p);
p /= sump;
double choice = rnd.NextDouble();
double s = 0;
for (int i = 0; i < p.Length(); i++)
{
s += p[i];
if (choice < s)
{
return(i);
}
}
// shouldn't happen...
return(costs.Length() - 1);
}
/// <summary>
/// Pick an array element with probability proportional to exp(-cost).
/// </summary>
public static int sample_by_costs(Floatarray costs)
{
Doublearray p = new Doublearray();
p.Copy(costs);
double mincost = NarrayUtil.Min(costs);
p -= mincost;
for (int i = 0; i < p.Length(); i++)
p.UnsafePut1d(i, Math.Exp(-p.UnsafeAt1d(i)));
double sump = NarrayUtil.Sum(p);
p /= sump;
double choice = rnd.NextDouble();
double s = 0;
for (int i = 0; i < p.Length(); i++)
{
s += p[i];
if (choice < s)
return i;
}
// shouldn't happen...
return costs.Length() - 1;
}
