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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.ranking.features.fieldmatch.reference;
import java.util.Arrays;
/**
* Implementation of optimal string alignment distance which also retains the four subdistances
* and which uses 2*query length memory rather than field length*query length.
* This class is not thread safe.
*
* @author bratseth
*/
public class OptimalStringAlignmentDistance {
/** The cell containg the last calculated edit distance */
private Cell value=new Cell(0,0,0,0);
// Temporary variables
private Cell[] thisRow, previousRow, previousPreviousRow;
private String[] query, field;
private boolean printTable=false;
public void calculate(String queryString,String fieldString) {
this.query=queryString.split(" ");
this.field=fieldString.split(" ");
thisRow=new Cell[query.length+1];
previousRow=new Cell[query.length+1];
previousPreviousRow=new Cell[query.length+1];
for(int i=0; i<=query.length; i++) {
thisRow[i]=new Cell(i+1,0,0,0);
previousRow[i]=new Cell(i,0,0,0);
previousPreviousRow[i]=new Cell(i-1,0,0,0);
}
print(previousRow);
for(int j=1;j<=field.length; j++) {
thisRow[0].setTo(0,j,0,0);
for(int i=1; i<=query.length; i++) {
setCell(i,j);
}
print(thisRow);
// Shift round thisRow -> previousRow -> previousPreviousRow -> thisRow
Cell[] temporaryRow=thisRow;
thisRow=previousPreviousRow;
previousPreviousRow=previousRow;
previousRow=temporaryRow;
}
value=previousRow[query.length];
}
private void setCell(int i,int j) {
Cell thisCell=thisRow[i];
Cell left=thisRow[i-1];
Cell above=previousRow[i];
Cell leftAbove=previousRow[i-1];
boolean substitution=!query[i-1].equals(field[j-1]);
int leftCost=left.getTotal()+1;
int aboveCost=above.getTotal()+1;
int leftAboveCost=leftAbove.getTotal() + ( substitution ? 1 : 0 );
if (leftCost<=aboveCost && leftCost<=leftAboveCost) {
thisCell.setTo(left);
thisCell.addDeletion();
}
else if (aboveCost<=leftCost && aboveCost<=leftAboveCost) {
thisCell.setTo(above);
thisCell.addInsertion();
}
else {
thisCell.setTo(leftAbove);
if (substitution)
thisCell.addSubstitution();
}
if (i>1 && j>1 && query[i-1].equals(field[j-2]) && query[i-2].equals(field[j-1]) ) {
Cell twoAboveAndLeft=previousPreviousRow[i-2];
int transpositionCost= + ( substitution ? 1 : 0);
if (transpositionCost<thisCell.getTotal()) {
thisCell.setTo(twoAboveAndLeft);
thisCell.addTransposition();
}
}
}
private void setCell(Cell thisCell,Cell left, Cell above, Cell leftAbove, boolean substitution) {
int a=left.getTotal()+1;
int b=above.getTotal()+1;
int c=leftAbove.getTotal();
c+=substitution ? 1 : 0;
if (a<=b && a<=c) {
thisCell.setTo(left);
thisCell.addDeletion();
}
else if (b<=a && b<=c) {
thisCell.setTo(above);
thisCell.addInsertion();
}
else {
thisCell.setTo(leftAbove);
if (substitution)
thisCell.addSubstitution();
}
/*
if(i > 1 and j > 1 and str1[i] = str2[j-1] and str1[i-1] = str2[j]) then
d[i, j] := minimum(
d[i, j],
d[i-2, j-2] + cost // transposition
)
*/
}
public float getTotal() { return value.getTotal(); }
public float getSubstitutions() { return value.getSubstitutions(); }
public float getDeletions() { return value.getDeletions(); }
public float getInsertions() { return value.getInsertions(); }
public float getTranspositions() { return value.getTranspositions(); }
/** Print the calculated edit distance table as we go */
public void setPrintTable(boolean printTable) {
this.printTable=printTable;
}
private void print(Cell[] row) {
if (!printTable) return;
for (Cell cell : row) {
System.out.print(cell.toShortString());
System.out.print(" ");
}
System.out.println();
}
/** Returns the current state as a string */
public String toString() {
StringBuffer b=new StringBuffer();
b.append("Query: " + Arrays.toString(query) + "\n");
b.append("Field: " + Arrays.toString(field) + "\n");
b.append(value);
return b.toString();
}
/** An edit distance table cell */
public static final class Cell {
private int deletions, insertions, substitutions, transpositions;
public Cell(int deletions,int insertions,int substitutions,int transpositions) {
setTo(deletions,insertions,substitutions,transpositions);
}
public void setTo(Cell cell) {
this.deletions=cell.deletions;
this.insertions=cell.insertions;
this.substitutions=cell.substitutions;
this.transpositions=cell.transpositions;
}
public void setTo(int deletions,int insertions,int substitutions,int transpositions) {
this.deletions=deletions;
this.insertions=insertions;
this.substitutions=substitutions;
this.transpositions=transpositions;
}
public int getTotal() {
return deletions+insertions+substitutions+transpositions;
}
public void addDeletion() { deletions++; }
public void addInsertion() { insertions++; }
public void addSubstitution() { substitutions++; }
public void addTransposition() { transpositions++; }
public int getDeletions() { return deletions; }
public int getInsertions() { return insertions; }
public int getSubstitutions() { return substitutions; }
public int getTranspositions() { return transpositions; }
public String toString() {
return "Total: " + getTotal() + ", substitutions: " + substitutions + ", deletions: " +
deletions + ", insertions: " + insertions + ", transpositions: " + transpositions + "\n";
}
public String toShortString() {
return "(" + substitutions + "," + deletions + "," + insertions + "," + transpositions + ")";
}
}
}
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