/// <summary>
/// Computes a single-mutation neighborhood (one param at a time) for a given configuration. For
/// numeric parameters, samples K mutations (i.e., creates K neighbors based on that paramater).
/// </summary>
/// <param name="parent">Starting configuration.</param>
/// <returns>A set of configurations that each differ from parent in exactly one parameter.</returns>
private ParameterSet[] GetOneMutationNeighborhood(ParameterSet parent)
{
List <ParameterSet> neighbors = new List <ParameterSet>();
SweeperProbabilityUtils spu = new SweeperProbabilityUtils(_host);
for (int i = 0; i < _sweepParameters.Length; i++)
{
// This allows us to query possible values of this parameter.
IValueGenerator sweepParam = _sweepParameters[i];
// This holds the actual value for this parameter, chosen in this parameter set.
IParameterValue pset = parent[sweepParam.Name];
_host.AssertValue(pset);
DiscreteValueGenerator parameterDiscrete = sweepParam as DiscreteValueGenerator;
if (parameterDiscrete != null)
{
// Create one neighbor for every discrete parameter.
Float[] neighbor = SweeperProbabilityUtils.ParameterSetAsFloatArray(_host, _sweepParameters, parent, false);
int hotIndex = -1;
for (int j = 0; j < parameterDiscrete.Count; j++)
{
if (parameterDiscrete[j].Equals(pset))
{
hotIndex = j;
break;
}
}
_host.Assert(hotIndex >= 0);
Random r = new Random();
int randomIndex = r.Next(0, parameterDiscrete.Count - 1);
randomIndex += randomIndex >= hotIndex ? 1 : 0;
neighbor[i] = randomIndex;
neighbors.Add(SweeperProbabilityUtils.FloatArrayAsParameterSet(_host, _sweepParameters, neighbor, false));
}
else
{
INumericValueGenerator parameterNumeric = sweepParam as INumericValueGenerator;
_host.Check(parameterNumeric != null, "SMAC sweeper can only sweep over discrete and numeric parameters");
// Create k neighbors (typically 4) for every numerical parameter.
for (int j = 0; j < _args.NumNeighborsForNumericalParams; j++)
{
Float[] neigh = SweeperProbabilityUtils.ParameterSetAsFloatArray(_host, _sweepParameters, parent, false);
double newVal = spu.NormalRVs(1, neigh[i], 0.2)[0];
while (newVal <= 0.0 || newVal >= 1.0)
{
newVal = spu.NormalRVs(1, neigh[i], 0.2)[0];
}
neigh[i] = (Float)newVal;
ParameterSet neighbor = SweeperProbabilityUtils.FloatArrayAsParameterSet(_host, _sweepParameters, neigh, false);
neighbors.Add(neighbor);
}
}
}
return(neighbors.ToArray());
}