smile.math.distance.HammingDistance Maven / Gradle / Ivy
/******************************************************************************
* Confidential Proprietary *
* (c) Copyright Haifeng Li 2011, All Rights Reserved *
******************************************************************************/
package smile.math.distance;
import java.util.BitSet;
/**
* In information theory, the Hamming distance between two strings of equal
* length is the number of positions for which the corresponding symbols are
* different. Put another way, it measures the minimum number of substitutions
* required to change one into the other, or the number of errors that
* transformed one string into the other. For a fixed length n, the Hamming
* distance is a metric on the vector space of the words of that length.
*
* @author Haifeng Li
*/
public class HammingDistance implements Metric {
/**
* Constructor.
*/
private HammingDistance() {
}
@Override
public String toString() {
return "Hamming distance";
}
/**
* Returns Hamming distance between the two arrays.
*/
@Override
public double d(T[] x, T[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
int dist = 0;
for (int i = 0; i < x.length; i++) {
if (!x[i].equals(y[i]))
dist++;
}
return dist;
}
/**
* Returns Hamming distance between the two bytes.
*/
public static int d(byte x, byte y) {
return d((int)x, (int)y);
}
/**
* Returns Hamming distance between the two shorts.
*/
public static int d(short x, short y) {
return d((int)x, (int)y);
}
/**
* Returns Hamming distance between the two integers.
*/
public static int d(int x, int y) {
int dist = 0;
int val = x ^ y;
// Count the number of set bits (Knuth's algorithm)
while (val != 0) {
++dist;
val &= val - 1;
}
return dist;
}
/**
* Returns Hamming distance between the two long integers.
*/
public static int d(long x, long y) {
int dist = 0;
long val = x ^ y;
// Count the number of set bits (Knuth's algorithm)
while (val != 0) {
++dist;
val &= val - 1;
}
return dist;
}
/**
* Returns Hamming distance between the two byte arrays.
*/
public static int d(byte[] x, byte[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
int dist = 0;
for (int i = 0; i < x.length; i++) {
if (x[i] != y[i])
dist++;
}
return dist;
}
/**
* Returns Hamming distance between the two short arrays.
*/
public static int d(short[] x, short[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
int dist = 0;
for (int i = 0; i < x.length; i++) {
if (x[i] != y[i])
dist++;
}
return dist;
}
/**
* Returns Hamming distance between the two integer arrays.
*/
public static int d(int[] x, int[] y) {
if (x.length != y.length)
throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
int dist = 0;
for (int i = 0; i < x.length; i++) {
if (x[i] != y[i])
dist++;
}
return dist;
}
/**
* Returns Hamming distance between the two BitSets.
*/
public static int d(BitSet x, BitSet y) {
if (x.size() != y.size())
throw new IllegalArgumentException(String.format("BitSets have different length: x[%d], y[%d]", x.size(), y.size()));
int dist = 0;
for (int i = 0; i < x.size(); i++) {
if (x.get(i) != y.get(i))
dist++;
}
return dist;
}
}