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Merged
merged 3 commits into from
Jul 9, 2025
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refactor: improve Sparsity class with input validation and clearer logic #6351

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refactor: improve Sparsity class with input validation and clearer logic
alxkm Jul 7, 2025
3deb276
Merge branch 'master' into refactor/sparsity
alxkm Jul 8, 2025
9335386
Merge branch 'master' into refactor/sparsity
DenizAltunkapan Jul 9, 2025
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50 changes: 28 additions & 22 deletions src/main/java/com/thealgorithms/misc/Sparsity.java
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Original file line number Diff line number Diff line change
@@ -1,40 +1,46 @@
package com.thealgorithms.misc;

/*
*A matrix is sparse if many of its coefficients are zero (In general if 2/3rd of matrix elements
*are 0, it is considered as sparse). The interest in sparsity arises because its exploitation can
*lead to enormous computational savings and because many large matrix problems that occur in
*practice are sparse.
/**
* Utility class for calculating the sparsity of a matrix.
* A matrix is considered sparse if a large proportion of its elements are zero.
* Typically, if more than 2/3 of the elements are zero, the matrix is considered sparse.
*
* @author Ojasva Jain
* Sparsity is defined as:
* sparsity = (number of zero elements) / (total number of elements)
*
* This can lead to significant computational optimizations.
*/
public final class Sparsity {

final class Sparsity {
private Sparsity() {
}

/*
* @param mat the input matrix
* @return Sparsity of matrix
*
* where sparsity = number of zeroes/total elements in matrix
/**
* Calculates the sparsity of a given 2D matrix.
*
* @param matrix the input matrix
* @return the sparsity value between 0 and 1
* @throws IllegalArgumentException if the matrix is null, empty, or contains empty rows
*/
static double sparsity(double[][] mat) {
if (mat == null || mat.length == 0) {
public static double sparsity(double[][] matrix) {
if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
throw new IllegalArgumentException("Matrix cannot be null or empty");
}

int zero = 0;
// Traversing the matrix to count number of zeroes
for (int i = 0; i < mat.length; i++) {
for (int j = 0; j < mat[i].length; j++) {
if (mat[i][j] == 0) {
zero++;
int zeroCount = 0;
int totalElements = 0;

// Count the number of zero elements and total elements
for (double[] row : matrix) {
for (double value : row) {
if (value == 0.0) {
zeroCount++;
}
totalElements++;
}
}
// return sparsity
return ((double) zero / (mat.length * mat[0].length));

// Return sparsity as a double
return (double) zeroCount / totalElements;
}
}
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