/**
* This is the "backscan-pruning" strategy described in the BIDE+ paper to avoid extending some
* prefixs that are guaranteed to not generate a closed pattern (see the BIDE+ paper for details).
*
* @param prefix the current prefix
* @param projectedContext the projected database
* @return boolean true if we should not extend the prefix
*/
private boolean checkBackScanPruning(
SequentialPattern prefix, List<PseudoSequenceBIDE> projectedContext) {
// DEBUGGIN
if (prefix.size() == 1 && prefix.get(0).get(0) == 5) {
System.out.println("PREFIX 5 ");
}
//
// See the BIDE+ paper for details about this method.
// For the number of item occurences that can be generated with this prefix:
for (int i = 0; i < prefix.getItemOccurencesTotalCount(); i++) {
Set<Integer> alreadyVisitedSID = new HashSet<Integer>();
// Create a Map of pairs to count the support of items (represented by a pair)
// in the ith semi-maximum periods
Map<PairBIDE, PairBIDE> mapPaires = new HashMap<PairBIDE, PairBIDE>();
// SOME CODE USED BY "findAllFrequentPairsForBackwardExtensionCheck"
Integer itemI = prefix.getIthItem(i); // iPeriod
Integer itemIm1 = null; // iPeriod -1
if (i > 0) {
itemIm1 = prefix.getIthItem(i - 1);
}
// // END NEW
// (1) For each i, we build the list of maximum periods
// for each sequence in the original database
for (PseudoSequenceBIDE pseudoSequence : projectedContext) {
int sequenceID = pseudoSequence.sequence.getId();
alreadyVisitedSID.add(pseudoSequence.sequence.getId());
Position currentCutPosition =
new Position(pseudoSequence.firstItemset, pseudoSequence.firstItem);
PseudoSequenceBIDE sequence = initialDatabase.get(sequenceID);
PseudoSequenceBIDE period =
sequence.getIthSemiMaximumPeriodOfAPrefix(prefix.getItemsets(), i, currentCutPosition);
if (period != null) {
// // we add it to the list of maximum periods
boolean hasExtension =
findAllFrequentPairsForBackwardExtensionCheck(
prefix.getAbsoluteSupport(),
prefix,
period,
i,
mapPaires,
itemI,
itemIm1,
currentCutPosition);
if (hasExtension) {
return true;
}
}
}
}
return false;
}
/**
* This is the "backscan-pruning" strategy described in the BIDE+ paper to avoid extending some
* prefixs that are guaranteed to not generate a closed pattern (see the BIDE+ paper for details).
*
* @param prefix the current prefix
* @return boolean true if we should not extend the prefix
*/
private boolean checkBackScanPruning(SequentialPattern prefix, Set<Integer> sidset) {
//
// See the BIDE+ paper for details about this method.
// For the number of item occurences that can be generated with this prefix:
for (int i = 0; i < prefix.getItemOccurencesTotalCount(); i++) {
Set<Integer> alreadyVisitedSID = new HashSet<Integer>();
// Create a Map of pairs to count the support of items (represented by a pair)
// in the ith semi-maximum periods
Map<PairBIDE, PairBIDE> mapPaires = new HashMap<PairBIDE, PairBIDE>();
// SOME CODE USED BY "findAllFrequentPairsForBackwardExtensionCheck"
Integer itemI = prefix.getIthItem(i); // iPeriod
Integer itemIm1 = null; // iPeriod -1
if (i > 0) {
itemIm1 = prefix.getIthItem(i - 1);
}
// // END NEW
int seqCount = 0;
// int highestSupportUntilNow = -1;
// (1) For each i, we build the list of maximum periods
// for each sequence in the original database
for (int sequenceID : sidset) {
alreadyVisitedSID.add(sequenceID);
PseudoSequenceBIDE sequence = initialDatabase.get(sequenceID);
PseudoSequenceBIDE period =
sequence.getIthSemiMaximumPeriodOfAPrefix(prefix.getItemsets(), i);
if (period != null) {
// // we add it to the list of maximum periods
boolean hasExtension =
findAllFrequentPairsForBackwardExtensionCheck(
alreadyVisitedSID.size(), prefix, period, i, mapPaires, itemI, itemIm1);
if (hasExtension) {
return true;
}
}
}
}
return false;
}
