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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.fsa.segmenter;
import java.util.LinkedList;
/**
* Contains the segmentation() method.
*
* @author Peter Boros
*/
public class Segments extends LinkedList<Segment> {
public final static int SEGMENTATION_WEIGHTED = 0;
public final static int SEGMENTATION_WEIGHTED_BIAS10 = 1;
public final static int SEGMENTATION_WEIGHTED_BIAS20 = 2;
public final static int SEGMENTATION_WEIGHTED_BIAS50 = 3;
public final static int SEGMENTATION_WEIGHTED_BIAS100 = 4;
public final static int SEGMENTATION_WEIGHTED_LEFTMOST = 5;
public final static int SEGMENTATION_WEIGHTED_RIGHTMOST = 6;
public final static int SEGMENTATION_WEIGHTED_LONGEST = 7;
public final static int SEGMENTATION_LEFTMOST_LONGEST = 8;
public final static int SEGMENTATION_LEFTMOST_WEIGHTED = 9;
public final static int SEGMENTATION_RIGHTMOST_LONGEST = 10;
public final static int SEGMENTATION_RIGHTMOST_WEIGHTED = 11;
public final static int SEGMENTATION_LONGEST_WEIGHTED = 12;
public final static int SEGMENTATION_LONGEST_LEFTMOST = 13;
public final static int SEGMENTATION_LONGEST_RIGHTMOST = 14;
public final static int SEGMENTATION_METHODS = 15;
private String[] _tokens;
private int _size;
private int[][] _map;
public Segments(String[] tokens)
{
_tokens = tokens;
_size = tokens.length;
_map = new int[_size+1][_size+1];
for(int i=0; i<=_size; i++){
for(int j=0; j<=_size; j++){
_map[i][j]=-1;
}
}
}
@Override
public boolean add(Segment s)
{
var result = super.add(s);
_map[s.beg()][s.end()]=super.size()-1;
return result;
}
private void addMissingSingles()
{
for(int i=0; i<_size; i++){
if(_map[i][i+1]==-1){
super.add(new Segment(i,i+1,0));
_map[i][i+1]=super.size()-1;
}
}
}
private void reMap()
{
for(int i=0; i<=_size; i++){
for(int j=0; j<=_size; j++){
_map[i][j]=-1;
}
}
for(int i=0; i<super.size(); i++){
_map[beg(i)][end(i)] = i;
}
}
public String sgm(int idx)
{
if(idx<0 || idx>=super.size()){
return null;
}
String s = new String(_tokens[super.get(idx).beg()]);
for(int i = super.get(idx).beg() + 1; i < super.get(idx).end(); i++){
s += " " + _tokens[i];
}
return s;
}
public int beg(int idx)
{
if(idx<0 || idx>=super.size()){
return -1;
}
return super.get(idx).beg();
}
public int end(int idx)
{
if(idx<0 || idx>=super.size()){
return -1;
}
return super.get(idx).end();
}
public int len(int idx)
{
if(idx<0 || idx>=super.size()){
return -1;
}
return super.get(idx).len();
}
public int conn(int idx)
{
if(idx<0 || idx>=super.size()){
return -1;
}
return super.get(idx).conn();
}
@SuppressWarnings("fallthrough")
public Segments segmentation(int method)
{
Segments smnt = new Segments(_tokens);
addMissingSingles();
int maxsc, id, bestid=-1, bias=0, c, pos, bestval, temp=0, next=-1;
int[] maxScore = new int[super.size()];
int[] nextid = new int[super.size()];
for(int i=0;i<nextid.length;i++){
nextid[i]=-1;
}
switch(method){
case SEGMENTATION_WEIGHTED_BIAS100:
bias+=50;
case SEGMENTATION_WEIGHTED_BIAS50:
bias+=30;
case SEGMENTATION_WEIGHTED_BIAS20:
bias+=10;
case SEGMENTATION_WEIGHTED_BIAS10:
bias+=10;
case SEGMENTATION_WEIGHTED:
bestid=-1;
for(int i=_tokens.length;i>=0;i--){
bestid=-1;maxsc=0;
for(int j=i+1;j<=_tokens.length;j++){
id=_map[i][j];
if(id>=0 && maxScore[id]+1>maxsc) {
bestid=id;
maxsc=maxScore[id]+1;
}
}
if(maxsc>0){
maxsc--;
}
for(int j=0;j<i;j++){
id=_map[j][i];
if(id>=0){
nextid[id] = bestid;
c = conn(id);
if(i-j<=1){
maxScore[id] = maxsc;
}
else if(bias>0){
maxScore[id] = maxsc + ((100+(i-j-2)*bias)*c)/100;
}
else{
maxScore[id] = maxsc + c;
}
}
}
}
id = bestid;
while(id!=-1){
smnt.add(super.get(id));
id=nextid[id];
}
break;
case SEGMENTATION_LEFTMOST_LONGEST:
case SEGMENTATION_LEFTMOST_WEIGHTED:
pos = 0;
while(pos<_tokens.length){
bestid = -1; bestval = -1;
for(int i=pos+1;i<=_tokens.length;i++){
id = _map[pos][i];
if(id>=0 &&
(method==SEGMENTATION_LEFTMOST_LONGEST ||
(temp=(len(id)>1)? conn(id) :0)>bestval) ){
bestid = id;
bestval = temp;
next = i;
}
}
smnt.add(super.get(bestid));
pos=next;
}
break;
case SEGMENTATION_RIGHTMOST_LONGEST:
case SEGMENTATION_RIGHTMOST_WEIGHTED:
pos = _tokens.length;
while(pos>0){
bestid = -1; bestval = -1;
for(int i=pos-1;i>=0;i--){
id = _map[i][pos];
if(id>=0 &&
(method==SEGMENTATION_RIGHTMOST_LONGEST ||
(temp=(len(id)>1)? conn(id) :0)>bestval) ){
bestid = id;
bestval = temp;
next = i;
}
}
smnt.addFirst(super.get(bestid));
pos=next;
}
smnt.reMap();
break;
case SEGMENTATION_LONGEST_WEIGHTED:
case SEGMENTATION_LONGEST_LEFTMOST:
case SEGMENTATION_LONGEST_RIGHTMOST:
case SEGMENTATION_WEIGHTED_LONGEST:
case SEGMENTATION_WEIGHTED_LEFTMOST:
case SEGMENTATION_WEIGHTED_RIGHTMOST:
buildSegmentationRecursive(method,smnt,0,_tokens.length);
break;
}
return smnt;
}
private void buildSegmentationRecursive(int method, Segments smnt, int b, int e)
{
int bestid, bestval1, bestval2, temp;
bestid=-1;bestval1=-1;bestval2=-1;
for(int i=0;i<super.size();i++){
if(b<=beg(i) && e>=end(i)){
switch(method){
case SEGMENTATION_LONGEST_WEIGHTED:
if(len(i)>bestval1 ||
(len(i)==bestval1 && conn(i)>bestval2) ){
bestid=i;
bestval1=len(i);
bestval2=conn(i);
}
break;
case SEGMENTATION_LONGEST_LEFTMOST:
if(len(i)>bestval1 ||
(len(i)==bestval1 && beg(i)<bestval2) ){
bestid=i;
bestval1=len(i);
bestval2=beg(i);
}
break;
case SEGMENTATION_LONGEST_RIGHTMOST:
if(len(i)>bestval1 ||
(len(i)==bestval1 && end(i)>bestval2) ){
bestid=i;
bestval1=len(i);
bestval2=end(i);
}
break;
case SEGMENTATION_WEIGHTED_LONGEST:
temp = (len(i)>1)?conn(i):0;
if(temp>bestval1 ||
(temp==bestval1 && len(i)>bestval2) ){
bestid=i;
bestval1=temp;
bestval2=len(i);
}
break;
case SEGMENTATION_WEIGHTED_LEFTMOST:
temp = (len(i)>1)? conn(i) :0;
if(temp>bestval1 ||
(temp==bestval1 && beg(i)<bestval2) ){
bestid=i;
bestval1=temp;
bestval2=beg(i);
}
break;
case SEGMENTATION_WEIGHTED_RIGHTMOST:
temp = len(i)>1?conn(i):0;
if(temp>bestval1 ||
(temp==bestval1 && end(i)>bestval2) ){
bestid=i;
bestval1=temp;
bestval2=end(i);
}
break;
default: // dummy defult pick first possible
if(bestid<0){
bestid=i;
}
break;
}
}
}
if(bestid<0) {
return; // this should never happen, as all one-word segments are created
}
if(b<beg(bestid)){
buildSegmentationRecursive(method,smnt,b,beg(bestid));
}
// add segment
smnt.add(super.get(bestid));
// check right side
if(e>end(bestid)){
buildSegmentationRecursive(method,smnt,end(bestid),e);
}
}
}
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