/**
* Method to find all frequent items in a projected sequence database
*
* @param sequences the set of sequences
* @return A list of pairs, where a pair is an item with (1) booleans indicating if it is in an
* itemset that is "cut" at left or right (prefix or postfix) and (2) the sequence IDs where
* it occurs.
*/
protected Set<PairBIDE> findAllFrequentPairs(
SequentialPattern prefix, List<PseudoSequenceBIDE> sequences) {
// We use a Map the store the pairs.
Map<PairBIDE, PairBIDE> mapPairs = new HashMap<PairBIDE, PairBIDE>();
// for each sequence
for (PseudoSequenceBIDE sequence : sequences) {
// for each itemset
for (int i = 0; i < sequence.size(); i++) {
// for each item
for (int j = 0; j < sequence.getSizeOfItemsetAt(i); j++) {
Integer item = sequence.getItemAtInItemsetAt(j, i);
// create the pair corresponding to this item
PairBIDE pair = new PairBIDE(sequence.isCutAtRight(i), sequence.isPostfix(i), item);
// register this sequenceID for that pair.
addPairWithoutCheck(mapPairs, sequence.getId(), pair);
}
}
}
// check the memory usage
MemoryLogger.getInstance().checkMemory();
return mapPairs.keySet(); // return the pairs.
}
/**
* Method to update the support count of item in a maximum period
*
* @param prefix the current prefix
* @param mapPaires
* @param maximum periods a maximum period
* @return a set of pairs indicating the support of items (note that a pair distinguish between
* items in a postfix, prefix...).
*/
protected boolean findAllFrequentPairsForBackwardExtensionCheck(
int seqProcessedCount,
SequentialPattern prefix,
PseudoSequenceBIDE maximumPeriod,
int iPeriod,
Map<PairBIDE, PairBIDE> mapPaires,
Integer itemI,
Integer itemIm1) {
int supportToMatch = prefix.getSequenceIDs().size();
int maxPeriodSize = maximumPeriod.size();
// for each itemset in that period
for (int i = 0; i < maxPeriodSize; i++) {
int sizeOfItemsetAtI = maximumPeriod.getSizeOfItemsetAt(i);
// NEW
boolean sawI = false; // sawI after current position
boolean sawIm1 = false; // sawI-1 before current position
// END NEW
// NEW march 20 2010 : check if I is after current position in current itemset
for (int j = 0; j < sizeOfItemsetAtI; j++) {
Integer item = maximumPeriod.getItemAtInItemsetAt(j, i);
if (item.equals(itemI)) {
sawI = true;
} else if (item > itemI) {
break;
}
}
// END NEW
for (int j = 0; j < sizeOfItemsetAtI; j++) {
Integer item = maximumPeriod.getItemAtInItemsetAt(j, i);
if (itemIm1 != null && item == itemIm1) {
sawIm1 = true;
}
boolean isPrefix = maximumPeriod.isCutAtRight(i);
boolean isPostfix = maximumPeriod.isPostfix(i);
// END NEW
PairBIDE paire = new PairBIDE(isPrefix, isPostfix, item);
if (seqProcessedCount >= minsuppAbsolute) {
// $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
// normal case
if (addPair(mapPaires, maximumPeriod.getId(), paire, supportToMatch)) {
return true;
}
// NEW: special cases
if (sawIm1) {
PairBIDE paire2 = new PairBIDE(isPrefix, !isPostfix, item);
if (addPair(mapPaires, maximumPeriod.getId(), paire2, supportToMatch)) {
return true;
}
}
if (sawI) {
PairBIDE paire2 = new PairBIDE(!isPrefix, isPostfix, item);
if (addPair(mapPaires, maximumPeriod.getId(), paire2, supportToMatch)) {
return true;
}
}
// END NEW
} else { // $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
// normal case
addPairWithoutCheck(mapPaires, maximumPeriod.getId(), paire);
// // NEW: special cases
if (sawIm1) {
PairBIDE paire2 = new PairBIDE(isPrefix, !isPostfix, item);
addPairWithoutCheck(mapPaires, maximumPeriod.getId(), paire2);
}
if (sawI) {
PairBIDE paire2 = new PairBIDE(!isPrefix, isPostfix, item);
addPairWithoutCheck(mapPaires, maximumPeriod.getId(), paire2);
}
// END NEW
}
}
}
return false;
}