Java Matrix Library by Arnav Merani

A numerically aware, row-major Java implementation of a fully functional matrix data structure supporting core linear algebra operations, structural queries, and explicit equality semantics. A high-performance, Maven-managed Linear Algebra library for Java 21 including end-to-end Javadoc and wide JUnit testing coverage.

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Features

• Matrix addition and subtraction
• Matrix multiplication
• Scalar multiplication
• Determinant computation (Gaussian elimination-based)
• Matrix inverse (Gauss–Jordan elimination with partial pivoting)
• Symmetric and skew-symmetric decomposition
• Structural queries (square, triangular, symmetric, identity, etc.)
• In-place and out-of-place operation variants
• Strict dimension and argument validation

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Numerical Design

• Structural and property checks use a configured floating-point tolerance (~1e-6) to account for rounding behavior.
• Pivot detection during elimination uses a stricter tolerance to handle near-singular matrices.
• equals() performs strict element-wise comparison using Double.compare (no tolerance).
• hashCode() is consistent with strict equality semantics.

This separation ensures numerical robustness while preserving the equals/hashCode contract.

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Mutability Model

• Methods ending with InPlace mutate the current instance.
• Non in-place methods return new Matrix instances and leave the original unchanged.
• Internal storage is deeply owned; external mutation is prevented via defensive copying.

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Getting Started

1. Install the Library Locally

Clone the repository and install the artifact into your local Maven repository:

   mvn clean install

This installs the library into:

  ~/.m2/repository/com/arnavmerani/matrix/1.0.1/

2. Add dependency to your project

Create a new project with the Maven build system, and add the following dependency to your pom.xml file:

<dependency>
    <groupId>com.arnavmerani</groupId>
    <artifactId>matrix</artifactId>
    <version>1.0.1</version>
</dependency>

Then reload Maven in your project using:

  mvn clean compile 

Usage Example

import com.arnavmerani.matrix.Matrix;

public class Main {
    public static void main(String[] args) {

        Matrix A = new Matrix(new double[][] {
            {1, 2},
            {3, 4}
        });

        Matrix B = A.inverse();
        double det = A.determinant();

        Matrix C = A.multiply(B);

        System.out.println("det(A) = " + det);
        System.out.println("A * A⁻¹ =");
        System.out.println(C);
    }
}

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License and Contact

• Maintainer: Arnav Merani
• GitHub: arnavmer-935
• License: MIT