private void Bide()
{
_allSequentialPatterns.Clear();
ProjectedDatabase projectedDatabase = _sequenceDatabase.ConvertToProjectedDatabase();
// Divides the search space according to frequent items and mine each recursively.
for (int i = 0; i < _1LengthSequentialPatterns.Count; ++i)
{
ProjectedDatabase freqItemProjectedDb = ConstructProjectedDatabase(_1LengthSequentialPatterns[i], projectedDatabase);
if (freqItemProjectedDb == null || !freqItemProjectedDb.IsNotEmpty)
{
continue;
}
if (ClosureChecker.BackScan(freqItemProjectedDb))
{
PrunedSequencesCount++;
}
else
{
Bide(freqItemProjectedDb);
}
}
}
/// <summary>
/// Checks if a given database contains some forward extensions items or backward extensions items.
/// </summary>
private static bool HasProjectedDatabaseAnyExtensions(ProjectedDatabase projectedDatabase, IEnumerable <Sequence> newSequentialPatterns)
{
// Checks if exist any forward extensions. If not tries find any backward extension
return(newSequentialPatterns.Any(sequence => sequence.Support == projectedDatabase.Prefix.Support)
||
ClosureChecker.BackwardExtensionCheck(projectedDatabase));
}
private void Bide(ProjectedDatabase projectedDatabase)
{
if (Stopped)
{
return;
}
_sExtensions.Clear();
_iExtensions.Clear();
// Scans projected database once and finds extension items.
projectedDatabase.FindLocalFrequentItems(_minSupport, _sExtensions, _iExtensions);
var newSequentialPatterns = new List <Sequence>();
// Sequence-extension items.
foreach (var pair in _sExtensions.OrderBy(e => e.Key))
{
newSequentialPatterns.Add(
Sequence.CreateNewBySStep(projectedDatabase.Prefix, pair.Key, pair.Value));
}
// Itemset-extension items.
foreach (var pair in _iExtensions.OrderBy(e => e.Key))
{
newSequentialPatterns.Add(
Sequence.CreateNewByIStep(projectedDatabase.Prefix, pair.Key, pair.Value));
}
// If projected database does not contain backward or forward extensions
// than a prefix of projection is closed sequential pattern.
if (!HasProjectedDatabaseAnyExtensions(projectedDatabase, newSequentialPatterns))
{
_allSequentialPatterns.Add(projectedDatabase.Prefix);
LogPattern(projectedDatabase.Prefix);
}
else
{
NoClosedSequencesCount++;
}
// Divides the search space and recursively mine the subset of all sequential patterns.
for (int i = 0; i < newSequentialPatterns.Count; ++i)
{
ProjectedDatabase seqPatternProjectedDatabase = ConstructProjectedDatabase(newSequentialPatterns[i], projectedDatabase);
if (seqPatternProjectedDatabase == null || !seqPatternProjectedDatabase.IsNotEmpty)
{
continue;
}
if (ClosureChecker.BackScan(seqPatternProjectedDatabase))
{
PrunedSequencesCount++;
}
else
{
Bide(seqPatternProjectedDatabase);
}
}
}