/// <summary>
/// Explores the input (sub-)space. Each invocation may return a different set.
/// </summary>
/// <returns>
/// A (reasonably-sized) stream of vectors/values from the (sub-)space.
/// </returns>
public override IEnumerable<Vector> Explore()
{
if (TargetMatrix.Dimensions.Count == 0)
{
// No dimensions to explore, then yield one empty vector.
yield return new Vector();
yield break;
}
ReadOnlyCollection<DimensionWithValues> dimensionValues = GetAllDimensionValues();
if (dimensionValues.Any(dim => dim.Values.Count == 0))
{
yield break; // One of the dimensions is empty
}
if (dimensionValues.Count < _order)
{
// This is really non-sensical to ask for an n-wise strategy for a matrix with less than n dimensions
// but I'd rather return a good default than throw. So I'll just cheat and do an exhaustive strategy instead
ExhaustiveCombinatorialStrategy exhaustiveStrategy = new ExhaustiveCombinatorialStrategy(this);
foreach (Vector v in exhaustiveStrategy.Explore())
yield return v;
yield break;
}
CoveredPairwiseCombinations coveredCombinations = new CoveredPairwiseCombinations();
DimensionValueIndexCombination currentCombination = new DimensionValueIndexCombination(dimensionValues);
DimensionIndexCombinationGenerator dimensionIndexGenerator = CreateDimensionIndexCombinationGenerator(dimensionValues);
Vector currentVector = currentCombination.GenerateVector();
if (IsValidVector(currentVector))
{
coveredCombinations.AddCoveredPairwiseCombinations(currentCombination, dimensionIndexGenerator);
yield return currentVector;
}
PartialVectorConstraintChecker partialConstraintChecker = UsePartialConstraintChecker ?
new PartialVectorConstraintChecker(dimensionValues, Constraints) : null;
foreach (ReadOnlyCollection<int> currentDimensionsToCover in dimensionIndexGenerator.Generate())
{
// Initialize the selection of values in the newly selected pairwise combination
for (int i = 0; i < currentDimensionsToCover.Count; i++)
{
currentCombination[currentDimensionsToCover[i]] = 0;
}
while (true)
{
bool selectionSucceeded = SelectNextValuesForCurrentDimensionCombination(currentCombination, currentDimensionsToCover);
if (!selectionSucceeded)
{
// We exhausted all combinations of values for the current pairwise combination
// select the next pairwise combination
break;
}
if (coveredCombinations.IsCombinationCovered(currentDimensionsToCover, currentCombination))
{
continue;
}
if (partialConstraintChecker != null &&
!partialConstraintChecker.IsValidForApplicableConstraints(currentCombination, currentDimensionsToCover))
{
// This combination is forbidden by constraints - carry on
continue;
}
// Randomize other values, try at most MAXTRIES since we might hit invalid combinations
for (int i = 0; i < MAXTRIES; i++)
{
List<int> remainingDimensionIndexes = Enumerable.Range(0, dimensionValues.Count)
.Where(di => !currentDimensionsToCover.Contains(di)) // Don't randomize the pair currently worked on
.ToList();
RandomUtilities.ShuffleList(remainingDimensionIndexes, _nextInt);
List<int> setDimensionIndexes = new List<int>(currentDimensionsToCover);
foreach (int dimensionIndex in remainingDimensionIndexes)
{
ReadOnlyCollection<int> allowedValueIndexes = UsePartialConstraintChecker ?
partialConstraintChecker.GetAllowedValueIndexesForDimension(dimensionIndex, setDimensionIndexes, currentCombination) :
Enumerable.Range(0, currentCombination.GetDimensionSize(dimensionIndex)).ToList().AsReadOnly();
if (allowedValueIndexes.Count == 0)
{
break;
}
currentCombination[dimensionIndex] = allowedValueIndexes[_nextInt(allowedValueIndexes.Count)];
setDimensionIndexes.Add(dimensionIndex);
}
if (setDimensionIndexes.Count < dimensionValues.Count)
{
// Couldn't set all dimension values, try again (or quit)
continue;
}
currentVector = currentCombination.GenerateVector();
if (partialConstraintChecker != null || IsValidVector(currentVector))
{
coveredCombinations.AddCoveredPairwiseCombinations(currentCombination, dimensionIndexGenerator);
yield return currentVector;
break; // Out of the MAXTRIES loop
}
}
}
}
}
