package ca.pfv.spmf.algorithms.sequentialpatterns.BIDE_and_prefixspan;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import ca.pfv.spmf.input.sequence_database_list_integers.Sequence;
import ca.pfv.spmf.input.sequence_database_list_integers.SequenceDatabase;
import ca.pfv.spmf.patterns.itemset_list_integers_without_support.Itemset;
import ca.pfv.spmf.tools.MemoryLogger;
/**
* This is the MaxSP algorithm that discovers
* the set of maximal sequential patterns instead of the set of all
* closed sequential patterns. It is described in the following paper:
*
* Fournier-Viger, P., Wu, C.-W., Tseng, V.-S. (2013). Mining Maximal Sequential
* Patterns without Candidate Maintenance. Proc. 9th International Conference
* on Advanced Data Mining and Applications (ADMA 2013) Part I, Springer
* LNAI 8346, pp. 169-180.
* *
* Copyright (c) 2008-2013 Philippe Fournier-Viger
*
* This file is part of the SPMF DATA MINING SOFTWARE
* (http://www.philippe-fournier-viger.com/spmf).
*
* SPMF is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* SPMF is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with SPMF. If not, see <http://www.gnu.org/licenses/>.
*/
public class AlgoMaxSP {
// for statistics
long startTime;
long endTime;
// the number of patterns found
int patternCount = 0;
// absolute minimum support
private int minsuppAbsolute;
// object to write the file
BufferedWriter writer = null;
// we have to keep a pointer to the original database
private Map<Integer, PseudoSequenceBIDE> initialDatabase = null; // sid, sequence
// The sequential patterns that are found
// (if the user want to keep them into memory)
private SequentialPatterns patterns = null;
/** if true, sequence identifiers of each pattern will be shown*/
boolean showSequenceIdentifiers = false;
//
//
// long debugFrequentPairsTime =0;
// long debugithPeriodTime =0;
// long debugAddPairTime =0;
// long debugProjectDBTime =0;
/**
* Default constructor
*/
public AlgoMaxSP(){
}
/**
* Run the algorithm
* @param database a sequence database
* @param outputPath an output file path
* @param minsup a minimum support as an integer representing a number of sequences
* @return return the result, if saved into memory, otherwise null
* @throws IOException exception if error while writing the file
*/
public SequentialPatterns runAlgorithm(SequenceDatabase database, String outputPath, int minsup) throws IOException {
// save minsup
this.minsuppAbsolute = minsup;
// reset the counter for the number of patterns found
patternCount = 0;
// reset the stats about memory usage
MemoryLogger.getInstance().reset();
// save the start time
startTime = System.currentTimeMillis();
// start the algorithm
maxSP(database, outputPath);
// save the end time
endTime = System.currentTimeMillis();
// close the output file if the result was saved to a file
if(writer != null){
writer.close();
}
return patterns;
}
/**
* This is the main method for the MaxSP algorithm.
* @param database a sequence database
* @throws IOException exception if some error occurs while writing the output file.
*/
private void maxSP(SequenceDatabase database, String outputFilePath) throws IOException{
// if the user want to keep the result into memory
if(outputFilePath == null){
writer = null;
patterns = new SequentialPatterns("FREQUENT SEQUENTIAL PATTERNS");
}else{ // if the user want to save the result to a file
patterns = null;
writer = new BufferedWriter(new FileWriter(outputFilePath));
}
// The algorithm first scan the database to find all frequent items
// The algorithm note the sequences in which these items appear.
// This is stored in a map: Key: item Value : IDs of sequences containing the item
Map<Integer, Set<Integer>> mapSequenceID = findSequencesContainingItems(database);
// WE CONVERT THE DATABASE TO A PSEUDO-DATABASE, AND REMOVE
// THE ITEMS OF SIZE 1 THAT ARE NOT FREQUENT, SO THAT THE ALGORITHM
// WILL NOT CONSIDER THEM ANYMORE.
// we create a database
initialDatabase = new HashMap<Integer, PseudoSequenceBIDE>();
// for each sequence of the original database
for(Sequence sequence : database.getSequences()){
// we make a copy of the sequence while removing infrequent items
Sequence optimizedSequence = sequence.cloneSequenceMinusItems(mapSequenceID, minsuppAbsolute);
if(optimizedSequence.size() != 0){
// if this sequence has size >0, we add it to the new database
initialDatabase.put(sequence.getId(), new PseudoSequenceBIDE(optimizedSequence, 0, 0));
}
}
// For each frequent item
loop1: for(Entry<Integer, Set<Integer>> entry : mapSequenceID.entrySet()){
// if the item is frequent
if(entry.getValue().size() >= minsuppAbsolute){
// build the projected database with this item
Integer item = entry.getKey();
List<PseudoSequenceBIDE> projectedContext = buildProjectedContextSingleItem(item, initialDatabase, false, entry.getValue());
// Create the prefix with this item
SequentialPattern prefix = new SequentialPattern();
prefix.addItemset(new Itemset(item));
// set the sequence IDS of this prefix
prefix.setSequenceIDs(entry.getValue());
// variable to store the largest support of patterns
// that will be found starting with this prefix
if(projectedContext.size() >= minsuppAbsolute) {
int successorSupport = 0;
// if(!checkBackScanPruning(prefix, entry.getValue())) {
successorSupport = recursion(prefix, projectedContext); // r�cursion;
// }
// else
// {
// System.out.println("back scan pruned " + prefix);
// }
// Finally, because this prefix has support > minsup
// and passed the backscan pruning,
// we check if it has no sucessor with support >= minsup
// (a forward extension)
// IF no forward extension
if(successorSupport < minsuppAbsolute){ // ######### MODIFICATION ####
// IF there is also no backward extension
if(!checkBackwardExtension(prefix, entry.getValue())){
// the pattern is closed and we save it
savePattern(prefix);
}
}
}else {
if(!checkBackwardExtension(prefix, entry.getValue())){
// the pattern is closed and we save it
savePattern(prefix);
}
}
}
}
// check the memory usage for statistics
MemoryLogger.getInstance().checkMemory();
}
/**
* Method to check if a prefix has a backward-extension (see Bide+ article for full details).
* This method do it a little bit differently than the BIDE+ article since
* we iterate with i on elements of the prefix instead of iterating with
* a i on the itemsets of the prefix. But the idea is the same!
* @param prefix the current prefix
* @return boolean true, if there is a backward extension
*/
private boolean checkBackwardExtension(SequentialPattern prefix, Set<Integer> sidset) {
// System.out.println("======" + prefix);
int totalOccurenceCount = prefix.getItemOccurencesTotalCount();
// For the ith item of the prefix
for(int i=0; i< totalOccurenceCount; i++){
Set<Integer> alreadyVisitedSID = new HashSet<Integer>();
// // 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
// 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>();
// (1) For each i, we build the list of maximum periods
// for each sequence in the original database
// int seqCount =0;
int highestSupportUntilNow = -1;
// 1703 pat - 9391 ms
for(int sequenceID : sidset){
// OPTIMIZATION PART 1== DON'T CHECK THE BACK EXTENSION IF THERE IS NOT ENOUGH SEQUENCE LEFT TO FIND AN EXTENSION
// THIS CAN IMPROVE THE PERFORMANCE BY UP TO 30% on FIFA
if(highestSupportUntilNow != -1 && highestSupportUntilNow + (sidset.size() - alreadyVisitedSID.size()) < minsuppAbsolute) {
break;
}
alreadyVisitedSID.add(sequenceID);
// END OF OPTIMIZATION PART 1 (IT CONTINUES A FEW LINES BELOW...)
PseudoSequenceBIDE sequence = initialDatabase.get(sequenceID);
PseudoSequenceBIDE period = sequence.getIthMaximumPeriodOfAPrefix(prefix.getItemsets(), i);
// if the period is not null
if(period !=null){
boolean hasBackwardExtension = findAllFrequentPairsForBackwardExtensionCheck(alreadyVisitedSID.size(), prefix, period, i, mapPaires, itemI, itemIm1);
if(hasBackwardExtension) {
// System.out.println(prefix + " has a backward extension from " + i + "th maxperiod in sequence from seq. " + sequenceID );
return true;
}
//===== OPTIMIZATION PART 2
if((sidset.size() - alreadyVisitedSID.size()) < minsuppAbsolute){
for(PairBIDE pair : mapPaires.values()) {
int supportOfPair = pair.getSequenceIDs().size();
if(supportOfPair > highestSupportUntilNow) {
highestSupportUntilNow = supportOfPair; // +1 because it may be raised for this sequence...
}
}
}
//===== END OF OPTIMIZATION PART 2
}
}
}
// totaltimeForBackwardExtension += System.currentTimeMillis() - start;
return false; // no backward extension, we 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;
// }
/**
* 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 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) {
// $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
// normal case
if(addPair(mapPaires, maximumPeriod.getId(),
paire)) {
return true;
}
// NEW: special cases
if(sawIm1){
PairBIDE paire2 = new PairBIDE(isPrefix, !isPostfix, item);
if(addPair(mapPaires, maximumPeriod.getId(),
paire2)) {
return true;
}
}
if(sawI ){
PairBIDE paire2 = new PairBIDE(!isPrefix, isPostfix, item);
if(addPair(mapPaires, maximumPeriod.getId(),
paire2)) {
return true;
}
}
// END NEW
}else { // $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$
// 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;
}
/**
* Add a pair to the map of pairs and add a sequence ID to it.
* If the pair is already in the map, the id is added to the old pair.
* @param mapPaires the map of pairs
* @param seqID a sequence id
* @param pair a pair
*/
private void addPairWithoutCheck(Map<PairBIDE, PairBIDE> mapPaires, Integer seqID, PairBIDE pair) {
// long start = System.currentTimeMillis();
// check if the pair is already in the map
PairBIDE oldPaire = mapPaires.get(pair);
// if not
if(oldPaire == null){
// we add the new pair "paire" to the map
mapPaires.put(pair, pair);
pair.getSequenceIDs().add(seqID);
}else{
// otherwise we use the old one
oldPaire.getSequenceIDs().add(seqID);
}
return;
}
private boolean addPair(Map<PairBIDE, PairBIDE> mapPaires, Integer seqID, PairBIDE pair) {
// long start = System.currentTimeMillis();
// check if the pair is already in the map
PairBIDE oldPaire = mapPaires.get(pair);
// if not
if(oldPaire == null){
// we add the new pair "paire" to the map
mapPaires.put(pair, pair);
}else{
// otherwise we use the old one
pair = oldPaire;
}
// we add the sequence ID to the pair
pair.getSequenceIDs().add(seqID);
if(pair.getSequenceIDs().size() >= minsuppAbsolute) {
return true;
}
// debugAddPairTime += System.currentTimeMillis() - start;
return false;
}
/**
* For each item, calculate the sequence id of sequences containing that item
* @param database the current sequence database
* @return Map of items to sequence IDs that contains each item
*/
private Map<Integer, Set<Integer>> findSequencesContainingItems(SequenceDatabase database) {
// We use a map to store the sequence IDs where an item appear
// Key : item Value : a set of sequence IDs
Map<Integer, Set<Integer>> mapSequenceID = new HashMap<Integer, Set<Integer>>(); // pour conserver les ID des s�quences: <Id Item, Set d'id de s�quences>
// for each sequence
for(Sequence sequence : database.getSequences()){
// for each itemset in that sequence
for(List<Integer> itemset : sequence.getItemsets()){
// for each item
for(Integer item : itemset){
// get the set of sequence ids for that item
Set<Integer> sequenceIDs = mapSequenceID.get(item);
if(sequenceIDs == null){
// if null create a new set
sequenceIDs = new HashSet<Integer>();
mapSequenceID.put(item, sequenceIDs);
}
// add the current sequence id to this set
sequenceIDs.add(sequence.getId());
}
}
}
return mapSequenceID;
}
//buildProjectedContextSingleItem
/**
* Create a projected database by pseudo-projection
* @param item The item to use to make the pseudo-projection
* @param context The current database.
* @param inSuffix This boolean indicates if the item "item" is part of a suffix or not.
* @return the projected database.
*/
private List<PseudoSequenceBIDE> buildProjectedContextSingleItem(Integer item, Map<Integer, PseudoSequenceBIDE> initialDatabase2, boolean inSuffix, Set<Integer> sidset) {
// The projected pseudo-database
List<PseudoSequenceBIDE> sequenceDatabase = new ArrayList<PseudoSequenceBIDE>();
// for each sequence
loop1:for(int sid: sidset){
PseudoSequenceBIDE sequence = initialDatabase2.get(sid);
// for each itemset of the sequence
for(int i =0; i< sequence.size(); i++){
int sizeOfItemsetAti = sequence.getSizeOfItemsetAt(i);
// find the position of the item used for the projection in this itemset if it appears
int index = sequence.indexOf(sizeOfItemsetAti, i, item);
// if it does appear and it is in a postfix/suffix if the item is in a postfix/suffix
if(index != -1 && sequence.isPostfix(i) == inSuffix){
// if this is not the last item of the itemset
if(index != sizeOfItemsetAti-1){
// create a new pseudo sequence
sequenceDatabase.add(new PseudoSequenceBIDE(sequence, i, index+1));
// continue loop1;
}else if (i != sequence.size()-1){// if this is not the last itemset of the sequence
// create a new pseudo sequence
// if the size of this pseudo sequence is greater than 0
// add it to the projected database.
sequenceDatabase.add(new PseudoSequenceBIDE( sequence, i+1, 0));
// continue loop1;
}
}
}
}
return sequenceDatabase; // return the projected database
}
/**
* Create a projected database by pseudo-projection
* @param item The item to use to make the pseudo-projection
* @param context The current database.
* @param inSuffix This boolean indicates if the item "item" is part of a suffix or not.
* @return the projected database.
*/
private List<PseudoSequenceBIDE> buildProjectedDatabase(Integer item, List<PseudoSequenceBIDE> database, boolean inSuffix, Set<Integer> sidset) {
// The projected pseudo-database
List<PseudoSequenceBIDE> sequenceDatabase = new ArrayList<PseudoSequenceBIDE>();
// for each sequence
loop1: for(PseudoSequenceBIDE sequence : database){
if(sidset.contains(sequence.getId()) == false){
continue;
}
// for each item of the sequence
for(int i =0; i< sequence.size(); i++){
int sizeOfItemsetAti = sequence.getSizeOfItemsetAt(i);
// check if the itemset contains the item that we use for the projection
int index = sequence.indexOf(sizeOfItemsetAti, i , item);
// if it does not, and the current item is part of a suffix if inSuffix is true
// and vice-versa
if(index != -1 && sequence.isPostfix(i) == inSuffix){
if(index != sizeOfItemsetAti - 1){ // if this is not the last item of the itemset
// create a new pseudo sequence
// add it to the projected database.
sequenceDatabase.add(new PseudoSequenceBIDE(sequence, i, index+1));
// continue loop1;
// }
}else if ((i != sequence.size()-1)){// if this is not the last itemset of the sequence
// create a new pseudo sequence
// add it to the projected database.
sequenceDatabase.add(new PseudoSequenceBIDE( sequence, i+1, 0));
// continue loop1;
}
}
}
}
return sequenceDatabase; // return the projected database
}
/**
* Method to recursively grow a given sequential pattern.
* @param prefix the current sequential pattern that we want to try to grow
* @param database the current projected sequence database
* @throws IOException exception if there is an error writing to the output file
*/
private int recursion(SequentialPattern prefix, List<PseudoSequenceBIDE> contexte) throws IOException {
// find frequent items of size 1 in the current projected database.
Set<PairBIDE> pairs = findAllFrequentPairs(prefix, contexte);
// we will keep tract of the maximum support of patterns
// that can be found with this prefix, to check
// for forward extension when this method returns.
int maxSupport = 0;
// For each pair found (a pair is an item with a boolean indicating if it
// appears in an itemset that is cut (a postfix) or not, and the sequence IDs
// where it appears in the projected database).
for(PairBIDE pair : pairs){
// if the item is frequent.
if(pair.getCount() >= minsuppAbsolute){
// create the new postfix by appending this item to the prefix
SequentialPattern newPrefix;
// if the item is part of a postfix
if(pair.isPostfix()){
// we append it to the last itemset of the prefix
newPrefix = appendItemToPrefixOfSequence(prefix, pair.getItem()); // is =<is, (deltaT,i)>
}else{ // else, we append it as a new itemset to the sequence
newPrefix = appendItemToSequence(prefix, pair.getItem());
}
// build the projected database with this item
// long start = System.currentTimeMillis();
List<PseudoSequenceBIDE> projectedContext = buildProjectedDatabase(pair.getItem(), contexte, pair.isPostfix(), pair.getSequenceIDs());
// debugProjectDBTime += System.currentTimeMillis() - start;
// create new prefix
newPrefix.setSequenceIDs(pair.getSequenceIDs());
// variable to keep track of the maximum support of extension
// with this item and this prefix
if(projectedContext.size() >= minsuppAbsolute) {
int maxSupportOfSuccessors = 0;
// if(!checkBackScanPruning(newPrefix, pair.getSequenceIDs())) {
maxSupportOfSuccessors = recursion(newPrefix, projectedContext); // r�cursion
// }
// check the forward extension for the prefix
// if no forward extension
if(minsuppAbsolute > maxSupportOfSuccessors){
// if there is no backward extension
if(!checkBackwardExtension(newPrefix, pair.getSequenceIDs())){
// save the pattern
savePattern(newPrefix);
}
}
}else {
if(!checkBackwardExtension(newPrefix, pair.getSequenceIDs())){
// save the pattern
savePattern(newPrefix);
}
}
// record the largest support of patterns found starting
// with this prefix until now
if(newPrefix.getAbsoluteSupport() > maxSupport){
maxSupport = newPrefix.getAbsoluteSupport();
}
}
}
return maxSupport; // return the maximum support generated by extension of the prefix
}
/**
* 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.
}
/**
* This method creates a copy of the sequence and add a given item
* as a new itemset to the sequence.
* It sets the support of the sequence as the support of the item.
* @param prefix the sequence
* @param item the item
* @return the new sequence
*/
private SequentialPattern appendItemToSequence(SequentialPattern prefix, Integer item) {
SequentialPattern newPrefix = prefix.cloneSequence(); // isSuffix
newPrefix.addItemset(new Itemset(item));
return newPrefix;
}
/**
* This method creates a copy of the sequence and add a given item
* to the last itemset of the sequence.
* It sets the support of the sequence as the support of the item.
* @param prefix the sequence
* @param item the item
* @return the new sequence
*/
private SequentialPattern appendItemToPrefixOfSequence(SequentialPattern prefix, Integer item) {
SequentialPattern newPrefix = prefix.cloneSequence();
// add to the last itemset
Itemset itemset = newPrefix.get(newPrefix.size()-1);
itemset.addItem(item);
return newPrefix;
}
/**
* This method saves a sequential pattern to the output file or
* in memory, depending on if the user provided an output file path or not
* when he launched the algorithm
* @param prefix the pattern to be saved.
* @throws IOException exception if error while writing the output file.
*/
private void savePattern(SequentialPattern prefix) throws IOException {
// increase the number of pattern found for statistics purposes
patternCount++;
// if the result should be saved to a file
if(writer != null){
StringBuilder r = new StringBuilder("");
for(Itemset itemset : prefix.getItemsets()){
// r.append('(');
for(Integer item : itemset.getItems()){
String string = item.toString();
r.append(string);
r.append(' ');
}
r.append("-1 ");
}
// // print the list of Pattern IDs that contains this pattern.
// if(prefix.getSequencesID() != null){
// r.append(" #SID: ");
// for(Integer id : prefix.getSequencesID()){
// r.append(id);
// r.append(' ');
// }
// }
r.append(" #SUP: ");
r.append(prefix.getSequenceIDs().size());
if(showSequenceIdentifiers) {
r.append(" #SID: ");
for (Integer sid: prefix.getSequenceIDs()) {
r.append(sid);
r.append(" ");
}
}
writer.write(r.toString());
writer.newLine();
}// otherwise the result is kept into memory
else{
patterns.addSequence(prefix, prefix.size());
}
}
/**
* Print statistics about the algorithm execution to System.out.
* @param size the size of the database
*/
public void printStatistics(int size) {
StringBuilder r = new StringBuilder(200);
r.append("============= Algorithm MaxSP - STATISTICS =============\n Total time ~ ");
r.append(endTime - startTime);
r.append(" ms\n");
r.append(" Maximal sequential pattern count : ");
r.append(patternCount);
r.append('\n');
r.append(" Max memory (mb):");
r.append(MemoryLogger.getInstance().getMaxMemory());
r.append('\n');
r.append("===================================================\n");
System.out.println(r.toString());
// System.out.println("Frequent pairs time : " + debugFrequentPairsTime);
// System.out.println("Generate ith period time: " + debugithPeriodTime);
// System.out.println("Add pair time: " + debugAddPairTime);
// System.out.println("Project DB time: " + debugProjectDBTime);
}
/**
* Set that the sequence identifiers should be shown (true) or not (false) for each
* pattern found
* @param showSequenceIdentifiers true or false
*/
public void setShowSequenceIdentifiers(boolean showSequenceIdentifiers) {
this.showSequenceIdentifiers = showSequenceIdentifiers;
}
}