/// <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()); }