public Rule?TryCreateRule(ReadOnlySpan <Rule> existingRules)
{
var seedsIndices = _seedSelector.FindSeedsIndices(existingRules);
if (seedsIndices.IsEmpty)
{
return(null);
}
var seedIndex = Random.Choice(seedsIndices);
var seed = _dataset.GetInstanceData(seedIndex);
var boxes = _boxConverter.FromRules(existingRules);
if (_runExpensiveSanityChecks)
{
for (int i = 0; i < boxes.Length; i++)
{
var box = boxes[i];
if (box.Contains(seed))
{
throw new InvalidOperationException();
}
}
}
var dimensionExpansionOrder = NaturalRange.CreateShuffled(
inclusiveStart: 0,
exclusiveEnd: _dataset.FeatureCount);
var secureRectangle = _boxCreator.TryCreateLargestNonIntersectingRectangle(
seedIndex: seedIndex,
existingHyperRectangles: boxes,
dimensionExpansionOrder: dimensionExpansionOrder);
if (secureRectangle is null)
{
return(null);
}
if (_runExpensiveSanityChecks)
{
for (int i = 0; i < boxes.Length; i++)
{
var box = boxes[i];
if (_rectangleIntersector.IntersectsInAllDimension(secureRectangle, box))
{
throw new InvalidOperationException();
}
}
}
var secureRectangleCoverage = _coverageComputer.ComputeCoverage(secureRectangle);
var coveredInstancesIndices = secureRectangleCoverage.IndicesOfCoveredInstances.ToArray();
if (coveredInstancesIndices.Length == 0)
{
return(null);
}
var coveredInstancesDistancesToSeed = _dataset.ComputeDistances(
targetInstanceIndex: seedIndex,
otherInstancesIndices: coveredInstancesIndices);
Array.Sort(
keys: coveredInstancesDistancesToSeed,
items: coveredInstancesIndices);
var instancesToCover = Math.Min(_targetNumberOfInstancesToCover, coveredInstancesIndices.Length);
var relevantInstances = coveredInstancesIndices
.AsSpan()
.Slice(start: 0, length: instancesToCover);
var ruleAntecedent = _antecedentCreator.CreateAntecedent(
seedIndex: seedIndex,
nearestInstancesIndices: relevantInstances);
if (ruleAntecedent is null)
{
return(null);
}
var ruleConsequent = _consequentCreator.CreateConsequent(relevantInstances);
return(new Rule(
antecedent: ruleAntecedent,
consequent: ruleConsequent));
}