public static List <ThresholdSubset> findThreshold(IEnumerable <QualifiedSubset> candidateSets, int k, int allparties, int NRSFT, bool findIntersection = true)
{
int allsentences = candidateSets.Count();
//add trace
attemptTrace.Add(string.Format("Set:{0}, Attempted threshold:({1},{2})", QualifiedSubset.DumpElementsIntoSingleString(candidateSets), k, allparties));
// normal case
List <ThresholdSubset> thresholds = new List <ThresholdSubset>();
var ncr = nCr(allparties, k);
if (ncr == allsentences)
{
ThresholdSubset th = new ThresholdSubset(allparties, k, new List <Trustee>(), QualifiedSubset.GetAllInvolvedParties(candidateSets).Parties);
thresholds.Add(th);
}
/// if the candidate set is larger than nCr then probably some sets don't belong to the threshold
/// Here we recusrively rotate parties and select all possible combinations to see which ones are
/// building threshold for e.g. p1p2p3 p2p3p4 p1p3p4 p1p2p4 p2p4p5
else if (allsentences < ncr)
{
if (NRSFT > allsentences)
{
NRSFT = GetNumberOfRequiredSetsForThreshold(allparties, k, allsentences);
}
if (NRSFT == 1)
{
return(thresholds);
}
//all possible candidate sets must be generated and recursively called
var smallersetcombinations = candidateSets.Combinations(NRSFT);
var subsetsAlreadyHaveThreshold = new List <QualifiedSubset>();
foreach (var smallerset in smallersetcombinations)
{
var newallparties = QualifiedSubset.GetAllInvolvedParties(smallerset).Parties.Count;
List <ThresholdSubset> foundthresholds = new List <ThresholdSubset>();
//add trace
attemptTrace.Add(string.Format("Set:{0}, Attempted threshold:({1},{2})",
QualifiedSubset.DumpElementsIntoSingleString(smallerset), k, newallparties));
if (nCr(newallparties, k) == smallerset.Count() && k < newallparties)//not interested in k=n thresholds
{
foundthresholds = findThreshold(smallerset, k, newallparties, NRSFT, findIntersection);
if (foundthresholds.Count > 0)
{
subsetsAlreadyHaveThreshold.AddRange(smallerset);
}
}
///try filtering the fixed sets maybe find a threshold
if (foundthresholds.Count == 0 && findIntersection)
{
foundthresholds = findFixedConcatThreshold(smallerset, k, newallparties, NRSFT);
}
if (foundthresholds != null)
{
thresholds.AddRange(foundthresholds);
}
}
if (--NRSFT > 1)
{
#if filterThresholds
var minusAlreadyFoundSets = candidateSets.Except(subsetsAlreadyHaveThreshold);
var minusSentences = minusAlreadyFoundSets.Count();
if (minusSentences < allsentences)
{
var minusInvolvedParties = QualifiedSubset.GetAllInvolvedParties(minusAlreadyFoundSets).Parties.Count;
//calculate new NRSFT
//NRSFT = GetNumberOfRequiredSetsForThreshold(minusInvolvedParties, k, minusAlreadyFoundSets.Count());
//if (NRSFT == 1) return thresholds;
}
thresholds.AddRange(findThreshold(minusAlreadyFoundSets, k, allparties, NRSFT, findIntersection));
#else
thresholds.AddRange(findThreshold(candidateSets, k, allparties, NRSFT, findIntersection));
#endif
}
}
return(thresholds);
}
public static List <ThresholdSubset> findFixedConcatThreshold(IEnumerable <QualifiedSubset> candidateSets, int k, int allparties, int NRSFT)
{
int allsentences = candidateSets.Count();
if (allsentences < 2)
{
return(null);
}
//fixed element normal case : just a fixed element in front of threshold candidates
var fixedIntersection = candidateSets.Select(po => po.Parties).Aggregate((first, second) => first.Intersect(second).ToList());
//add trace
fixedAttemptTrace.Add(string.Format("Set:{0}, Attempted fixed item:{1} + threshold:({2},{3})", QualifiedSubset.DumpElementsIntoSingleString(candidateSets)
, new QualifiedSubset(fixedIntersection).ToString(), k, allparties));
if (fixedIntersection.Count > 0)
{
var smallerQS = new List <QualifiedSubset>();
//remove fixed part from parties and try to find normal threshold
foreach (var qs in candidateSets)
{
var withoutFixedParties = qs.Parties.Except(fixedIntersection);
if (withoutFixedParties.Count() > 0)
{
var tempqs = new QualifiedSubset(withoutFixedParties);
smallerQS.Add(tempqs);
}
}
var smallerQSinvolvedParties = QualifiedSubset.GetAllInvolvedParties(smallerQS).Parties.Count;
var smallerK = k - fixedIntersection.Count;
if (nCr(smallerQSinvolvedParties, smallerK) == allsentences)
{
var threshold = findThreshold(smallerQS, smallerK, smallerQSinvolvedParties, NRSFT, false);
if (threshold != null)
//now add the fixed part to the threshold
{
foreach (var th in threshold)
{
th.fixedParties = fixedIntersection;
}
return(threshold);
}
}
}
return(new List <ThresholdSubset>());
}
