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);
}
}
}
/// <summary>
/// Converts sequence database to the projected sequence database.
/// </summary>
internal ProjectedDatabase ConvertToProjectedDatabase()
{
var projectedDatabase = new ProjectedDatabase();
for (int sid = 0, j = this.Count; sid < j; ++sid)
{
projectedDatabase.Add(new PseudoSequence(this[sid]));
}
return(projectedDatabase);
}
private void PrefixSpan(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));
}
// Divides the search space and recursively mine the subset of all sequential patterns.
for (int i = 0; i < newSequentialPatterns.Count; ++i)
{
Sequence seqPattern = newSequentialPatterns[i];
_allSequentialPatterns.Add(seqPattern);
LogPattern(seqPattern);
ProjectedDatabase seqPatternProjectedDatabase = ConstructProjectedDatabase(seqPattern, projectedDatabase);
if (seqPatternProjectedDatabase == null || !seqPatternProjectedDatabase.IsNotEmpty) continue;
PrefixSpan(seqPatternProjectedDatabase);
}
}
private ProjectedDatabase ConstructProjectedDatabase(Sequence prefix, ProjectedDatabase database)
{
var prefixLastItem = prefix.LastItem;
var projectedDatabase = new ProjectedDatabase(prefix);
// The count of sequences in a database which dont have to contains prefix
// and projected database can still contains some sequential pattern.
var minSequencesInProjectedDb = database.Size - (int)_minSupport;
for (int sid = 0, lastSid = database.Size; sid < lastSid; sid++)
{
// If sequence contains the last item of a prefix, project sequence and add it to db.
int itemsetIndex;
if ((itemsetIndex = database[sid].Contains(prefixLastItem)) >= 0)
{
var pseudoSequence = PseudoSequence.MakeProjection(database[sid], prefix, itemsetIndex, false);
if (pseudoSequence != null)
{
projectedDatabase.Add(pseudoSequence);
continue;
}
}
// If projected database can not contains new sequential pattern stop projection sooner.
if (--minSequencesInProjectedDb >= 0)
{
continue;
}
return(null);
}
return(projectedDatabase);
}
/// <summary>
/// Checks if a given database contains backward-S-extension event.
/// </summary>
private static bool BackwardSExtensionCheck(ProjectedDatabase projectedDatabase)
{
var lastInLastAppearances = new int[projectedDatabase.Count];
var seqMaximumPeriod = new HashSet <uint>();
for (int i = projectedDatabase.Prefix.Size - 1; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var ithMaximumPeriod = default(HashSet <uint>);
var isIthMaximumPeriodEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
// The i-th maximum period of a prefix sequence is defined:
// 1) 1 < i <= n: it is the piece of sequence between the end
// of the first instance of prefix e1e2...ei-1 and LLi.
// 2) i == 1: it is the piece of sequence located before the first last-in-last appearance (LL1).
int lastInLast = sequence.GetLastInLast(ei, lastInLastAppearances[sid]);
lastInLastAppearances[sid] = lastInLast;
// If i-th maximum period is empty just continue fill in lastInLastAppearances for the checking (i-1)-th maximum period.
if (isIthMaximumPeriodEmpty)
{
continue;
}
int firstInstance = 0;
if (i != 0)
{
firstInstance = sequence.GetFirstInstance(i) + 1;
}
seqMaximumPeriod.Clear();
for (; firstInstance < lastInLast; firstInstance++)
{
seqMaximumPeriod.UnionWith(sequence.RawItems[firstInstance]);
}
// ScanSkip:
if (ithMaximumPeriod == null)
{
ithMaximumPeriod = new HashSet <uint>(seqMaximumPeriod);
}
else
{
ithMaximumPeriod.IntersectWith(seqMaximumPeriod);
}
// If i-th maximum period is empty and i==0 there cant exist any backward-S-extensions,
// otherwise if i>0, try find backward-S-extensions in (i-1)-th maximum period.
if (ithMaximumPeriod.Count != 0)
{
continue;
}
if (i == 0)
{
return(false);
}
isIthMaximumPeriodEmpty = true;
}
// If all i-th maximum periods (in every sequence) contains any items, we got a backward-S-extension.
if (ithMaximumPeriod.Count != 0)
{
return(true);
}
}
return(false);
}
private ProjectedDatabase ConstructProjectedDatabase(Sequence prefix, ProjectedDatabase sourceProjectedDatabase)
{
var prefixLastItem = prefix.LastItem;
var projectedDatabase = new ProjectedDatabase(prefix);
// The count of sequences in a database which dont have to contains prefix
// and projected database can still contains some sequential pattern.
int minSequencesInProjectedDb = sourceProjectedDatabase.Size - (int) _minSupport;
for (int sid = 0, lastSid = sourceProjectedDatabase.Size; sid < lastSid; sid++)
{
// If sequence contains the last item of a prefix, project sequence and add it to db.
int itemsetIndex;
if ((itemsetIndex = sourceProjectedDatabase[sid].Contains(prefixLastItem)) >= 0)
{
var pseudoSequence = PseudoSequence.MakeProjection(sourceProjectedDatabase[sid], prefix, itemsetIndex);
if (pseudoSequence != null && pseudoSequence.IsNotEmpty)
{
projectedDatabase.Add(pseudoSequence);
continue;
}
}
// If projected database can not contains new sequential pattern stop projection sooner.
if (--minSequencesInProjectedDb < 0) return null;
}
return projectedDatabase;
}
/// <summary>
/// Checks if a given database contains backward-I-extension event.
/// </summary>
private static bool BackwardIExtensionCheck(ProjectedDatabase projectedDatabase)
{
var lastInLastAppearances = new int[projectedDatabase.Count];
var seqBackwardIExtensionItemset = new HashSet<uint>();
for (int i = projectedDatabase.Prefix.Size - 1; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var ithBackwardIExtensionItemset = default(HashSet<uint>);
var isIthBackwardIExtensionItemsetEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
// The i-th I-extensions period of a prefix sequence is defined:
// 1) 1 < i <= n: it is the piece of sequence between the end
// of the first instance of prefix e1e2..ei-1
// and the beginning of the first event after the LLi.
// 2) i == 1: it is the piece of sequence located before the first event after LL1.
int lastInLast = sequence.GetLastInLast(ei, lastInLastAppearances[sid]);
lastInLastAppearances[sid] = lastInLast;
// If ith maximum period is empty just continue fill in lastInLastAppearances for the checking (i-1)-th maximum period.
if (isIthBackwardIExtensionItemsetEmpty) continue;
int firstInstance = 0;
if (i != 0) firstInstance = sequence.GetFirstInstance(i) + 1;
seqBackwardIExtensionItemset.Clear();
for (; firstInstance <= lastInLast; firstInstance++)
{
if (ei.IsSubsetOf(sequence.RawItems[firstInstance]))
{
seqBackwardIExtensionItemset.UnionWith(sequence.RawItems[firstInstance]);
}
}
seqBackwardIExtensionItemset.ExceptWith(ei);
// ScanSkip:
if (ithBackwardIExtensionItemset == null)
{
ithBackwardIExtensionItemset = new HashSet<uint>(seqBackwardIExtensionItemset);
}
else
{
ithBackwardIExtensionItemset.IntersectWith(seqBackwardIExtensionItemset);
}
// If ith maximum period is empty and i==0 there cant exist any backward-I-extension,
// otherwise if i>0, try find backward-I-extension in (i-1)-th maximum period.
if (ithBackwardIExtensionItemset.Count != 0) continue;
if (i == 0) return false;
isIthBackwardIExtensionItemsetEmpty = true;
}
// If all ith maximum periods (in every sequence) contains some items we got a backward-I-extension.
if (ithBackwardIExtensionItemset.Count > 0) return true;
}
return false;
}
/// <summary>
/// Returns TRUE if a prefix of projection can be safely pruned.
/// </summary>
public static bool BackScan(ProjectedDatabase projectedDatabase)
{
return BackScanS(projectedDatabase) || BackScanI(projectedDatabase);
}
/// <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);
}
/// <summary>
/// Returns TRUE if a prefix of projection can be safely pruned.
/// </summary>
public static bool BackScan(ProjectedDatabase projectedDatabase)
{
return(BackScanS(projectedDatabase) || BackScanI(projectedDatabase));
}
/// <summary>
/// Checks if a given database contains backward-S-extension event.
/// </summary>
private static bool BackwardSExtensionCheck(ProjectedDatabase projectedDatabase)
{
var lastInLastAppearances = new int[projectedDatabase.Count];
var seqMaximumPeriod = new HashSet<uint>();
for (int i = projectedDatabase.Prefix.Size - 1; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var ithMaximumPeriod = default(HashSet<uint>);
var isIthMaximumPeriodEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
// The i-th maximum period of a prefix sequence is defined:
// 1) 1 < i <= n: it is the piece of sequence between the end
// of the first instance of prefix e1e2...ei-1 and LLi.
// 2) i == 1: it is the piece of sequence located before the first last-in-last appearance (LL1).
int lastInLast = sequence.GetLastInLast(ei, lastInLastAppearances[sid]);
lastInLastAppearances[sid] = lastInLast;
// If i-th maximum period is empty just continue fill in lastInLastAppearances for the checking (i-1)-th maximum period.
if (isIthMaximumPeriodEmpty) continue;
int firstInstance = 0;
if (i != 0) firstInstance = sequence.GetFirstInstance(i) + 1;
seqMaximumPeriod.Clear();
for (; firstInstance < lastInLast; firstInstance++)
{
seqMaximumPeriod.UnionWith(sequence.RawItems[firstInstance]);
}
// ScanSkip:
if (ithMaximumPeriod == null)
{
ithMaximumPeriod = new HashSet<uint>(seqMaximumPeriod);
}
else
{
ithMaximumPeriod.IntersectWith(seqMaximumPeriod);
}
// If i-th maximum period is empty and i==0 there cant exist any backward-S-extensions,
// otherwise if i>0, try find backward-S-extensions in (i-1)-th maximum period.
if (ithMaximumPeriod.Count != 0) continue;
if (i == 0) return false;
isIthMaximumPeriodEmpty = true;
}
// If all i-th maximum periods (in every sequence) contains any items, we got a backward-S-extension.
if (ithMaximumPeriod.Count != 0) return true;
}
return false;
}
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);
}
}
}
private static bool BackScanI(ProjectedDatabase projectedDatabase)
{
var lastInFirstAppearances = new int[projectedDatabase.Count];
var seqSemiMaximumPeriod = new HashSet <uint>();
var n = projectedDatabase.Prefix.Size - 1;
for (int i = n; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var eiLastItemId = ei.Last();
var ithSemiMaximumPeriod = default(HashSet <uint>);
var isIthSemiMaximumPeriodEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
int lastInFirst = sequence.GetLastInFirst(i, ei, lastInFirstAppearances[sid]);
lastInFirstAppearances[sid] = lastInFirst;
// If i-th semimaximum period is empty just continue fill in lastInFirstAppearances for the checking (i-1)-th semimaximum period.
if (isIthSemiMaximumPeriodEmpty)
{
continue;
}
int firstInstance = 0;
if (i != 0)
{
firstInstance = sequence.GetFirstInstance(i) + 1;
}
seqSemiMaximumPeriod.Clear();
for (; firstInstance <= lastInFirst; firstInstance++)
{
if (!ei.IsSubsetOf(sequence.RawItems[firstInstance]))
{
continue;
}
seqSemiMaximumPeriod.UnionWith(
i == n
? sequence.RawItems[firstInstance].Where(a => a < eiLastItemId)
: sequence.RawItems[firstInstance]);
}
seqSemiMaximumPeriod.ExceptWith(ei);
// ScanSkip:
if (ithSemiMaximumPeriod == null)
{
ithSemiMaximumPeriod = new HashSet <uint>(seqSemiMaximumPeriod);
}
else
{
ithSemiMaximumPeriod.IntersectWith(seqSemiMaximumPeriod);
}
// If i-th maximum period is empty and i==0 there cant exist any backward-S-extensions,
// otherwise if i>0, try find backward-S-extensions in (i-1)-th maximum period.
if (ithSemiMaximumPeriod.Count != 0)
{
continue;
}
if (i == 0)
{
return(false);
}
isIthSemiMaximumPeriodEmpty = true;
}
// If all i-th maximum periods (in every sequence) contains any items, we got a backward-S-extension.
if (ithSemiMaximumPeriod.Count != 0)
{
return(true);
}
}
return(false);
}
/// <summary>
/// Checks if a given database contains some backward-extension event.
/// </summary>
public static bool BackwardExtensionCheck(ProjectedDatabase projectedDatabase)
{
return(BackwardSExtensionCheck(projectedDatabase) || BackwardIExtensionCheck(projectedDatabase));
}
private static bool BackScanI(ProjectedDatabase projectedDatabase)
{
var lastInFirstAppearances = new int[projectedDatabase.Count];
var seqSemiMaximumPeriod = new HashSet<uint>();
var n = projectedDatabase.Prefix.Size - 1;
for (int i = n; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var eiLastItemId = ei.Last();
var ithSemiMaximumPeriod = default(HashSet<uint>);
var isIthSemiMaximumPeriodEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
int lastInFirst = sequence.GetLastInFirst(i, ei, lastInFirstAppearances[sid]);
lastInFirstAppearances[sid] = lastInFirst;
// If i-th semimaximum period is empty just continue fill in lastInFirstAppearances for the checking (i-1)-th semimaximum period.
if (isIthSemiMaximumPeriodEmpty) continue;
int firstInstance = 0;
if (i != 0) firstInstance = sequence.GetFirstInstance(i) + 1;
seqSemiMaximumPeriod.Clear();
for (; firstInstance <= lastInFirst; firstInstance++)
{
if (!ei.IsSubsetOf(sequence.RawItems[firstInstance])) continue;
seqSemiMaximumPeriod.UnionWith(
i == n
? sequence.RawItems[firstInstance].Where(a => a < eiLastItemId)
: sequence.RawItems[firstInstance]);
}
seqSemiMaximumPeriod.ExceptWith(ei);
// ScanSkip:
if (ithSemiMaximumPeriod == null)
{
ithSemiMaximumPeriod = new HashSet<uint>(seqSemiMaximumPeriod);
}
else
{
ithSemiMaximumPeriod.IntersectWith(seqSemiMaximumPeriod);
}
// If i-th maximum period is empty and i==0 there cant exist any backward-S-extensions,
// otherwise if i>0, try find backward-S-extensions in (i-1)-th maximum period.
if (ithSemiMaximumPeriod.Count != 0) continue;
if (i == 0) return false;
isIthSemiMaximumPeriodEmpty = true;
}
// If all i-th maximum periods (in every sequence) contains any items, we got a backward-S-extension.
if (ithSemiMaximumPeriod.Count != 0) return true;
}
return false;
}
/// <summary>
/// Checks if a given database contains backward-I-extension event.
/// </summary>
private static bool BackwardIExtensionCheck(ProjectedDatabase projectedDatabase)
{
var lastInLastAppearances = new int[projectedDatabase.Count];
var seqBackwardIExtensionItemset = new HashSet <uint>();
for (int i = projectedDatabase.Prefix.Size - 1; i >= 0; i--)
{
var ei = projectedDatabase.Prefix[i];
var ithBackwardIExtensionItemset = default(HashSet <uint>);
var isIthBackwardIExtensionItemsetEmpty = false;
for (int sid = 0; sid < projectedDatabase.Count; sid++)
{
PseudoSequence sequence = projectedDatabase[sid];
// The i-th I-extensions period of a prefix sequence is defined:
// 1) 1 < i <= n: it is the piece of sequence between the end
// of the first instance of prefix e1e2..ei-1
// and the beginning of the first event after the LLi.
// 2) i == 1: it is the piece of sequence located before the first event after LL1.
int lastInLast = sequence.GetLastInLast(ei, lastInLastAppearances[sid]);
lastInLastAppearances[sid] = lastInLast;
// If ith maximum period is empty just continue fill in lastInLastAppearances for the checking (i-1)-th maximum period.
if (isIthBackwardIExtensionItemsetEmpty)
{
continue;
}
int firstInstance = 0;
if (i != 0)
{
firstInstance = sequence.GetFirstInstance(i) + 1;
}
seqBackwardIExtensionItemset.Clear();
for (; firstInstance <= lastInLast; firstInstance++)
{
if (ei.IsSubsetOf(sequence.RawItems[firstInstance]))
{
seqBackwardIExtensionItemset.UnionWith(sequence.RawItems[firstInstance]);
}
}
seqBackwardIExtensionItemset.ExceptWith(ei);
// ScanSkip:
if (ithBackwardIExtensionItemset == null)
{
ithBackwardIExtensionItemset = new HashSet <uint>(seqBackwardIExtensionItemset);
}
else
{
ithBackwardIExtensionItemset.IntersectWith(seqBackwardIExtensionItemset);
}
// If ith maximum period is empty and i==0 there cant exist any backward-I-extension,
// otherwise if i>0, try find backward-I-extension in (i-1)-th maximum period.
if (ithBackwardIExtensionItemset.Count != 0)
{
continue;
}
if (i == 0)
{
return(false);
}
isIthBackwardIExtensionItemsetEmpty = true;
}
// If all ith maximum periods (in every sequence) contains some items we got a backward-I-extension.
if (ithBackwardIExtensionItemset.Count > 0)
{
return(true);
}
}
return(false);
}
/// <summary>
/// Checks if a given database contains some backward-extension event.
/// </summary>
public static bool BackwardExtensionCheck(ProjectedDatabase projectedDatabase)
{
return BackwardSExtensionCheck(projectedDatabase) || BackwardIExtensionCheck(projectedDatabase);
}
