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source: trunk/CrossPare/src/de/ugoe/cs/cpdp/training/WekaLocalFQTraining.java @ 116

Last change on this file since 116 was 99, checked in by sherbold, 9 years ago
improved error reporting
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1	// Copyright 2015 Georg-August-Universität Göttingen, Germany
2	//
3	// Licensed under the Apache License, Version 2.0 (the "License");
4	// you may not use this file except in compliance with the License.
5	// You may obtain a copy of the License at
6	//
7	// http://www.apache.org/licenses/LICENSE-2.0
8	//
9	// Unless required by applicable law or agreed to in writing, software
10	// distributed under the License is distributed on an "AS IS" BASIS,
11	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12	// See the License for the specific language governing permissions and
13	// limitations under the License.
14
15	package de.ugoe.cs.cpdp.training;
16
17	import java.util.ArrayList;
18	import java.util.HashMap;
19	import java.util.HashSet;
20	import java.util.Iterator;
21	import java.util.Random;
22	import java.util.Set;
23	import java.util.logging.Level;
24
25	import de.ugoe.cs.cpdp.training.QuadTree;
26	import de.ugoe.cs.util.console.Console;
27	import weka.classifiers.AbstractClassifier;
28	import weka.classifiers.Classifier;
29	import weka.core.DenseInstance;
30	import weka.core.EuclideanDistance;
31	import weka.core.Instance;
32	import weka.core.Instances;
33	import weka.filters.Filter;
34	import weka.filters.unsupervised.attribute.Remove;
35
36	/**
37	* Trainer with reimplementation of WHERE clustering algorithm from: Tim Menzies, Andrew Butcher,
38	* David Cok, Andrian Marcus, Lucas Layman, Forrest Shull, Burak Turhan, Thomas Zimmermann,
39	* "Local versus Global Lessons for Defect Prediction and Effort Estimation," IEEE Transactions on
40	* Software Engineering, vol. 39, no. 6, pp. 822-834, June, 2013
41	*
42	* With WekaLocalFQTraining we do the following: 1) Run the Fastmap algorithm on all training data,
43	* let it calculate the 2 most significant dimensions and projections of each instance to these
44	* dimensions 2) With these 2 dimensions we span a QuadTree which gets recursively split on
45	* median(x) and median(y) values. 3) We cluster the QuadTree nodes together if they have similar
46	* density (50%) 4) We save the clusters and their training data 5) We only use clusters with >
47	* ALPHA instances (currently Math.sqrt(SIZE)), rest is discarded with the training data of this
48	* cluster 6) We train a Weka classifier for each cluster with the clusters training data 7) We
49	* recalculate Fastmap distances for a single instance with the old pivots and then try to find a
50	* cluster containing the coords of the instance. 7.1.) If we can not find a cluster (due to coords
51	* outside of all clusters) we find the nearest cluster. 8) We classify the Instance with the
52	* classifier and traindata from the Cluster we found in 7.
53	*/
54	public class WekaLocalFQTraining extends WekaBaseTraining implements ITrainingStrategy {
55
56	private final TraindatasetCluster classifier = new TraindatasetCluster();
57
58	@Override
59	public Classifier getClassifier() {
60	return classifier;
61	}
62
63	@Override
64	public void apply(Instances traindata) {
65	try {
66	classifier.buildClassifier(traindata);
67	}
68	catch (Exception e) {
69	throw new RuntimeException(e);
70	}
71	}
72
73	public class TraindatasetCluster extends AbstractClassifier {
74
75	private static final long serialVersionUID = 1L;
76
77	/* classifier per cluster */
78	private HashMap<Integer, Classifier> cclassifier;
79
80	/* instances per cluster */
81	private HashMap<Integer, Instances> ctraindata;
82
83	/*
84	* holds the instances and indices of the pivot objects of the Fastmap calculation in
85	* buildClassifier
86	*/
87	private HashMap<Integer, Instance> cpivots;
88
89	/* holds the indices of the pivot objects for x,y and the dimension [x,y][dimension] */
90	private int[][] cpivotindices;
91
92	/* holds the sizes of the cluster multiple "boxes" per cluster */
93	private HashMap<Integer, ArrayList<Double[][]>> csize;
94
95	/* debug vars */
96	@SuppressWarnings("unused")
97	private boolean show_biggest = true;
98
99	@SuppressWarnings("unused")
100	private int CFOUND = 0;
101	@SuppressWarnings("unused")
102	private int CNOTFOUND = 0;
103
104	private Instance createInstance(Instances instances, Instance instance) {
105	// attributes for feeding instance to classifier
106	Set<String> attributeNames = new HashSet<>();
107	for (int j = 0; j < instances.numAttributes(); j++) {
108	attributeNames.add(instances.attribute(j).name());
109	}
110
111	double[] values = new double[instances.numAttributes()];
112	int index = 0;
113	for (int j = 0; j < instance.numAttributes(); j++) {
114	if (attributeNames.contains(instance.attribute(j).name())) {
115	values[index] = instance.value(j);
116	index++;
117	}
118	}
119
120	Instances tmp = new Instances(instances);
121	tmp.clear();
122	Instance instCopy = new DenseInstance(instance.weight(), values);
123	instCopy.setDataset(tmp);
124
125	return instCopy;
126	}
127
128	/**
129	* Because Fastmap saves only the image not the values of the attributes it used we can not
130	* use the old data directly to classify single instances to clusters.
131	*
132	* To classify a single instance we do a new fastmap computation with only the instance and
133	* the old pivot elements.
134	*
135	* After that we find the cluster with our fastmap result for x and y.
136	*/
137	@Override
138	public double classifyInstance(Instance instance) {
139
140	double ret = 0;
141	try {
142	// classinstance gets passed to classifier
143	Instances traindata = ctraindata.get(0);
144	Instance classInstance = createInstance(traindata, instance);
145
146	// this one keeps the class attribute
147	Instances traindata2 = ctraindata.get(1);
148
149	// remove class attribute before clustering
150	Remove filter = new Remove();
151	filter.setAttributeIndices("" + (traindata.classIndex() + 1));
152	filter.setInputFormat(traindata);
153	traindata = Filter.useFilter(traindata, filter);
154	Instance clusterInstance = createInstance(traindata, instance);
155
156	Fastmap FMAP = new Fastmap(2);
157	EuclideanDistance dist = new EuclideanDistance(traindata);
158
159	// we set our pivot indices [x=0,y=1][dimension]
160	int[][] npivotindices = new int[2][2];
161	npivotindices[0][0] = 1;
162	npivotindices[1][0] = 2;
163	npivotindices[0][1] = 3;
164	npivotindices[1][1] = 4;
165
166	// build temp dist matrix (2 pivots per dimension + 1 instance we want to classify)
167	// the instance we want to classify comes first after that the pivot elements in the
168	// order defined above
169	double[][] distmat = new double[2 * FMAP.target_dims + 1][2 * FMAP.target_dims + 1];
170	distmat[0][0] = 0;
171	distmat[0][1] =
172	dist.distance(clusterInstance,
173	this.cpivots.get((Integer) this.cpivotindices[0][0]));
174	distmat[0][2] =
175	dist.distance(clusterInstance,
176	this.cpivots.get((Integer) this.cpivotindices[1][0]));
177	distmat[0][3] =
178	dist.distance(clusterInstance,
179	this.cpivots.get((Integer) this.cpivotindices[0][1]));
180	distmat[0][4] =
181	dist.distance(clusterInstance,
182	this.cpivots.get((Integer) this.cpivotindices[1][1]));
183
184	distmat[1][0] =
185	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][0]),
186	clusterInstance);
187	distmat[1][1] = 0;
188	distmat[1][2] =
189	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][0]),
190	this.cpivots.get((Integer) this.cpivotindices[1][0]));
191	distmat[1][3] =
192	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][0]),
193	this.cpivots.get((Integer) this.cpivotindices[0][1]));
194	distmat[1][4] =
195	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][0]),
196	this.cpivots.get((Integer) this.cpivotindices[1][1]));
197
198	distmat[2][0] =
199	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][0]),
200	clusterInstance);
201	distmat[2][1] =
202	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][0]),
203	this.cpivots.get((Integer) this.cpivotindices[0][0]));
204	distmat[2][2] = 0;
205	distmat[2][3] =
206	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][0]),
207	this.cpivots.get((Integer) this.cpivotindices[0][1]));
208	distmat[2][4] =
209	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][0]),
210	this.cpivots.get((Integer) this.cpivotindices[1][1]));
211
212	distmat[3][0] =
213	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][1]),
214	clusterInstance);
215	distmat[3][1] =
216	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][1]),
217	this.cpivots.get((Integer) this.cpivotindices[0][0]));
218	distmat[3][2] =
219	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][1]),
220	this.cpivots.get((Integer) this.cpivotindices[1][0]));
221	distmat[3][3] = 0;
222	distmat[3][4] =
223	dist.distance(this.cpivots.get((Integer) this.cpivotindices[0][1]),
224	this.cpivots.get((Integer) this.cpivotindices[1][1]));
225
226	distmat[4][0] =
227	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][1]),
228	clusterInstance);
229	distmat[4][1] =
230	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][1]),
231	this.cpivots.get((Integer) this.cpivotindices[0][0]));
232	distmat[4][2] =
233	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][1]),
234	this.cpivots.get((Integer) this.cpivotindices[1][0]));
235	distmat[4][3] =
236	dist.distance(this.cpivots.get((Integer) this.cpivotindices[1][1]),
237	this.cpivots.get((Integer) this.cpivotindices[0][1]));
238	distmat[4][4] = 0;
239
240	/*
241	* debug output: show biggest distance found within the new distance matrix double
242	* biggest = 0; for(int i=0; i < distmat.length; i++) { for(int j=0; j <
243	* distmat[0].length; j++) { if(biggest < distmat[i][j]) { biggest = distmat[i][j];
244	* } } } if(this.show_biggest) { Console.traceln(Level.INFO,
245	* String.format(""+clusterInstance)); Console.traceln(Level.INFO,
246	* String.format("biggest distances: "+ biggest)); this.show_biggest = false; }
247	*/
248
249	FMAP.setDistmat(distmat);
250	FMAP.setPivots(npivotindices);
251	FMAP.calculate();
252	double[][] x = FMAP.getX();
253	double[] proj = x[0];
254
255	// debug output: show the calculated distance matrix, our result vektor for the
256	// instance and the complete result matrix
257	/*
258	* Console.traceln(Level.INFO, "distmat:"); for(int i=0; i<distmat.length; i++){
259	* for(int j=0; j<distmat[0].length; j++){ Console.trace(Level.INFO,
260	* String.format("%20s", distmat[i][j])); } Console.traceln(Level.INFO, ""); }
261	*
262	* Console.traceln(Level.INFO, "vector:"); for(int i=0; i < proj.length; i++) {
263	* Console.trace(Level.INFO, String.format("%20s", proj[i])); }
264	* Console.traceln(Level.INFO, "");
265	*
266	* Console.traceln(Level.INFO, "resultmat:"); for(int i=0; i<x.length; i++){ for(int
267	* j=0; j<x[0].length; j++){ Console.trace(Level.INFO, String.format("%20s",
268	* x[i][j])); } Console.traceln(Level.INFO, ""); }
269	*/
270
271	// now we iterate over all clusters (well, boxes of sizes per cluster really) and
272	// save the number of the
273	// cluster in which we are
274	int cnumber;
275	int found_cnumber = -1;
276	Iterator<Integer> clusternumber = this.csize.keySet().iterator();
277	while (clusternumber.hasNext() && found_cnumber == -1) {
278	cnumber = clusternumber.next();
279
280	// now iterate over the boxes of the cluster and hope we find one (cluster could
281	// have been removed)
282	// or we are too far away from any cluster because of the fastmap calculation
283	// with the initial pivot objects
284	for (int box = 0; box < this.csize.get(cnumber).size(); box++) {
285	Double[][] current = this.csize.get(cnumber).get(box);
286
287	if (proj[0] >= current[0][0] && proj[0] <= current[0][1] && // x
288	proj[1] >= current[1][0] && proj[1] <= current[1][1])
289	{ // y
290	found_cnumber = cnumber;
291	}
292	}
293	}
294
295	// we want to count how often we are really inside a cluster
296	// if ( found_cnumber == -1 ) {
297	// CNOTFOUND += 1;
298	// }else {
299	// CFOUND += 1;
300	// }
301
302	// now it can happen that we do not find a cluster because we deleted it previously
303	// (too few instances)
304	// or we get bigger distance measures from weka so that we are completely outside of
305	// our clusters.
306	// in these cases we just find the nearest cluster to our instance and use it for
307	// classification.
308	// to do that we use the EuclideanDistance again to compare our distance to all
309	// other Instances
310	// then we take the cluster of the closest weka instance
311	dist = new EuclideanDistance(traindata2);
312	if (!this.ctraindata.containsKey(found_cnumber)) {
313	double min_distance = Double.MAX_VALUE;
314	clusternumber = ctraindata.keySet().iterator();
315	while (clusternumber.hasNext()) {
316	cnumber = clusternumber.next();
317	for (int i = 0; i < ctraindata.get(cnumber).size(); i++) {
318	if (dist.distance(instance, ctraindata.get(cnumber).get(i)) <= min_distance)
319	{
320	found_cnumber = cnumber;
321	min_distance =
322	dist.distance(instance, ctraindata.get(cnumber).get(i));
323	}
324	}
325	}
326	}
327
328	// here we have the cluster where an instance has the minimum distance between
329	// itself and the
330	// instance we want to classify
331	// if we still have not found a cluster we exit because something is really wrong
332	if (found_cnumber == -1) {
333	Console.traceln(Level.INFO, String
334	.format("ERROR matching instance to cluster with full search!"));
335	throw new RuntimeException("cluster not found with full search");
336	}
337
338	// classify the passed instance with the cluster we found and its training data
339	ret = cclassifier.get(found_cnumber).classifyInstance(classInstance);
340
341	}
342	catch (Exception e) {
343	Console.traceln(Level.INFO, String.format("ERROR matching instance to cluster!"));
344	throw new RuntimeException(e);
345	}
346	return ret;
347	}
348
349	@Override
350	public void buildClassifier(Instances traindata) throws Exception {
351
352	// Console.traceln(Level.INFO, String.format("found: "+ CFOUND + ", notfound: " +
353	// CNOTFOUND));
354	this.show_biggest = true;
355
356	cclassifier = new HashMap<Integer, Classifier>();
357	ctraindata = new HashMap<Integer, Instances>();
358	cpivots = new HashMap<Integer, Instance>();
359	cpivotindices = new int[2][2];
360
361	// 1. copy traindata
362	Instances train = new Instances(traindata);
363	Instances train2 = new Instances(traindata); // this one keeps the class attribute
364
365	// 2. remove class attribute for clustering
366	Remove filter = new Remove();
367	filter.setAttributeIndices("" + (train.classIndex() + 1));
368	filter.setInputFormat(train);
369	train = Filter.useFilter(train, filter);
370
371	// 3. calculate distance matrix (needed for Fastmap because it starts at dimension 1)
372	double biggest = 0;
373	EuclideanDistance dist = new EuclideanDistance(train);
374	double[][] distmat = new double[train.size()][train.size()];
375	for (int i = 0; i < train.size(); i++) {
376	for (int j = 0; j < train.size(); j++) {
377	distmat[i][j] = dist.distance(train.get(i), train.get(j));
378	if (distmat[i][j] > biggest) {
379	biggest = distmat[i][j];
380	}
381	}
382	}
383	// Console.traceln(Level.INFO, String.format("biggest distances: "+ biggest));
384
385	// 4. run fastmap for 2 dimensions on the distance matrix
386	Fastmap FMAP = new Fastmap(2);
387	FMAP.setDistmat(distmat);
388	FMAP.calculate();
389
390	cpivotindices = FMAP.getPivots();
391
392	double[][] X = FMAP.getX();
393
394	// quadtree payload generation
395	ArrayList<QuadTreePayload<Instance>> qtp = new ArrayList<QuadTreePayload<Instance>>();
396
397	// we need these for the sizes of the quadrants
398	double[] big =
399	{ 0, 0 };
400	double[] small =
401	{ Double.MAX_VALUE, Double.MAX_VALUE };
402
403	// set quadtree payload values and get max and min x and y values for size
404	for (int i = 0; i < X.length; i++) {
405	if (X[i][0] >= big[0]) {
406	big[0] = X[i][0];
407	}
408	if (X[i][1] >= big[1]) {
409	big[1] = X[i][1];
410	}
411	if (X[i][0] <= small[0]) {
412	small[0] = X[i][0];
413	}
414	if (X[i][1] <= small[1]) {
415	small[1] = X[i][1];
416	}
417	QuadTreePayload<Instance> tmp =
418	new QuadTreePayload<Instance>(X[i][0], X[i][1], train2.get(i));
419	qtp.add(tmp);
420	}
421
422	// Console.traceln(Level.INFO,
423	// String.format("size for cluster ("+small[0]+","+small[1]+") - ("+big[0]+","+big[1]+")"));
424
425	// 5. generate quadtree
426	QuadTree TREE = new QuadTree(null, qtp);
427	QuadTree.size = train.size();
428	QuadTree.alpha = Math.sqrt(train.size());
429	QuadTree.ccluster = new ArrayList<ArrayList<QuadTreePayload<Instance>>>();
430	QuadTree.csize = new HashMap<Integer, ArrayList<Double[][]>>();
431
432	// Console.traceln(Level.INFO, String.format("Generate QuadTree with "+ QuadTree.size +
433	// " size, Alpha: "+ QuadTree.alpha+ ""));
434
435	// set the size and then split the tree recursively at the median value for x, y
436	TREE.setSize(new double[]
437	{ small[0], big[0] }, new double[]
438	{ small[1], big[1] });
439
440	// recursive split und grid clustering eher static
441	TREE.recursiveSplit(TREE);
442
443	// generate list of nodes sorted by density (childs only)
444	ArrayList<QuadTree> l = new ArrayList<QuadTree>(TREE.getList(TREE));
445
446	// recursive grid clustering (tree pruning), the values are stored in ccluster
447	TREE.gridClustering(l);
448
449	// wir iterieren durch die cluster und sammeln uns die instanzen daraus
450	// ctraindata.clear();
451	for (int i = 0; i < QuadTree.ccluster.size(); i++) {
452	ArrayList<QuadTreePayload<Instance>> current = QuadTree.ccluster.get(i);
453
454	// i is the clusternumber
455	// we only allow clusters with Instances > ALPHA, other clusters are not considered!
456	// if(current.size() > QuadTree.alpha) {
457	if (current.size() > 4) {
458	for (int j = 0; j < current.size(); j++) {
459	if (!ctraindata.containsKey(i)) {
460	ctraindata.put(i, new Instances(train2));
461	ctraindata.get(i).delete();
462	}
463	ctraindata.get(i).add(current.get(j).getInst());
464	}
465	}
466	else {
467	Console.traceln(Level.INFO,
468	String.format("drop cluster, only: " + current.size() +
469	" instances"));
470	}
471	}
472
473	// here we keep things we need later on
474	// QuadTree sizes for later use (matching new instances)
475	this.csize = new HashMap<Integer, ArrayList<Double[][]>>(QuadTree.csize);
476
477	// pivot elements
478	// this.cpivots.clear();
479	for (int i = 0; i < FMAP.PA[0].length; i++) {
480	this.cpivots.put(FMAP.PA[0][i], (Instance) train.get(FMAP.PA[0][i]).copy());
481	}
482	for (int j = 0; j < FMAP.PA[0].length; j++) {
483	this.cpivots.put(FMAP.PA[1][j], (Instance) train.get(FMAP.PA[1][j]).copy());
484	}
485
486	/*
487	* debug output int pnumber; Iterator<Integer> pivotnumber =
488	* cpivots.keySet().iterator(); while ( pivotnumber.hasNext() ) { pnumber =
489	* pivotnumber.next(); Console.traceln(Level.INFO, String.format("pivot: "+pnumber+
490	* " inst: "+cpivots.get(pnumber))); }
491	*/
492
493	// train one classifier per cluster, we get the cluster number from the traindata
494	int cnumber;
495	Iterator<Integer> clusternumber = ctraindata.keySet().iterator();
496	// cclassifier.clear();
497
498	// int traindata_count = 0;
499	while (clusternumber.hasNext()) {
500	cnumber = clusternumber.next();
501	cclassifier.put(cnumber, setupClassifier()); // this is the classifier used for the
502	// cluster
503	cclassifier.get(cnumber).buildClassifier(ctraindata.get(cnumber));
504	// Console.traceln(Level.INFO, String.format("classifier in cluster "+cnumber));
505	// traindata_count += ctraindata.get(cnumber).size();
506	// Console.traceln(Level.INFO,
507	// String.format("building classifier in cluster "+cnumber +" with "+
508	// ctraindata.get(cnumber).size() +" traindata instances"));
509	}
510
511	// add all traindata
512	// Console.traceln(Level.INFO, String.format("traindata in all clusters: " +
513	// traindata_count));
514	}
515	}
516
517	/**
518	* Payload for the QuadTree. x and y are the calculated Fastmap values. T is a weka instance.
519	*/
520	public class QuadTreePayload<T> {
521
522	public double x;
523	public double y;
524	private T inst;
525
526	public QuadTreePayload(double x, double y, T value) {
527	this.x = x;
528	this.y = y;
529	this.inst = value;
530	}
531
532	public T getInst() {
533	return this.inst;
534	}
535	}
536
537	/**
538	* Fastmap implementation
539	*
540	* Faloutsos, C., & Lin, K. I. (1995). FastMap: A fast algorithm for indexing, data-mining and
541	* visualization of traditional and multimedia datasets (Vol. 24, No. 2, pp. 163-174). ACM.
542	*/
543	public class Fastmap {
544
545	/* N x k Array, at the end, the i-th row will be the image of the i-th object */
546	private double[][] X;
547
548	/* 2 x k pivot Array one pair per recursive call */
549	private int[][] PA;
550
551	/* Objects we got (distance matrix) */
552	private double[][] O;
553
554	/* column of X currently updated (also the dimension) */
555	private int col = 0;
556
557	/* number of dimensions we want */
558	private int target_dims = 0;
559
560	// if we already have the pivot elements
561	private boolean pivot_set = false;
562
563	public Fastmap(int k) {
564	this.target_dims = k;
565	}
566
567	/**
568	* Sets the distance matrix and params that depend on this
569	*
570	* @param O
571	*/
572	public void setDistmat(double[][] O) {
573	this.O = O;
574	int N = O.length;
575	this.X = new double[N][this.target_dims];
576	this.PA = new int[2][this.target_dims];
577	}
578
579	/**
580	* Set pivot elements, we need that to classify instances after the calculation is complete
581	* (because we then want to reuse only the pivot elements).
582	*
583	* @param pi
584	*/
585	public void setPivots(int[][] pi) {
586	this.pivot_set = true;
587	this.PA = pi;
588	}
589
590	/**
591	* Return the pivot elements that were chosen during the calculation
592	*
593	* @return
594	*/
595	public int[][] getPivots() {
596	return this.PA;
597	}
598
599	/**
600	* The distance function for euclidean distance
601	*
602	* Acts according to equation 4 of the fastmap paper
603	*
604	* @param x
605	* x index of x image (if k==0 x object)
606	* @param y
607	* y index of y image (if k==0 y object)
608	* @param kdimensionality
609	* @return distance
610	*/
611	private double dist(int x, int y, int k) {
612
613	// basis is object distance, we get this from our distance matrix
614	double tmp = this.O[x][y] * this.O[x][y];
615
616	// decrease by projections
617	for (int i = 0; i < k; i++) {
618	double tmp2 = (this.X[x][i] - this.X[y][i]);
619	tmp -= tmp2 * tmp2;
620	}
621
622	return Math.abs(tmp);
623	}
624
625	/**
626	* Find the object farthest from the given index This method is a helper Method for
627	* findDistandObjects
628	*
629	* @param index
630	* of the object
631	* @return index of the farthest object from the given index
632	*/
633	private int findFarthest(int index) {
634	double furthest = Double.MIN_VALUE;
635	int ret = 0;
636
637	for (int i = 0; i < O.length; i++) {
638	double dist = this.dist(i, index, this.col);
639	if (i != index && dist > furthest) {
640	furthest = dist;
641	ret = i;
642	}
643	}
644	return ret;
645	}
646
647	/**
648	* Finds the pivot objects
649	*
650	* This method is basically algorithm 1 of the fastmap paper.
651	*
652	* @return 2 indexes of the choosen pivot objects
653	*/
654	private int[] findDistantObjects() {
655	// 1. choose object randomly
656	Random r = new Random();
657	int obj = r.nextInt(this.O.length);
658
659	// 2. find farthest object from randomly chosen object
660	int idx1 = this.findFarthest(obj);
661
662	// 3. find farthest object from previously farthest object
663	int idx2 = this.findFarthest(idx1);
664
665	return new int[]
666	{ idx1, idx2 };
667	}
668
669	/**
670	* Calculates the new k-vector values (projections)
671	*
672	* This is basically algorithm 2 of the fastmap paper. We just added the possibility to
673	* pre-set the pivot elements because we need to classify single instances after the
674	* computation is already done.
675	*
676	* @param dims
677	* dimensionality
678	*/
679	public void calculate() {
680
681	for (int k = 0; k < this.target_dims; k++) {
682	// 2) choose pivot objects
683	if (!this.pivot_set) {
684	int[] pivots = this.findDistantObjects();
685
686	// 3) record ids of pivot objects
687	this.PA[0][this.col] = pivots[0];
688	this.PA[1][this.col] = pivots[1];
689	}
690
691	// 4) inter object distances are zero (this.X is initialized with 0 so we just
692	// continue)
693	if (this.dist(this.PA[0][this.col], this.PA[1][this.col], this.col) == 0) {
694	continue;
695	}
696
697	// 5) project the objects on the line between the pivots
698	double dxy = this.dist(this.PA[0][this.col], this.PA[1][this.col], this.col);
699	for (int i = 0; i < this.O.length; i++) {
700
701	double dix = this.dist(i, this.PA[0][this.col], this.col);
702	double diy = this.dist(i, this.PA[1][this.col], this.col);
703
704	double tmp = (dix + dxy - diy) / (2 * Math.sqrt(dxy));
705
706	// save the projection
707	this.X[i][this.col] = tmp;
708	}
709
710	this.col += 1;
711	}
712	}
713
714	/**
715	* returns the result matrix of the projections
716	*
717	* @return calculated result
718	*/
719	public double[][] getX() {
720	return this.X;
721	}
722	}
723	}

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