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Jeometry, a Mathematic and Geometry library for Java
There is a newer version: 1.0.5
package org.jeometry.math.solver;

import org.jeometry.Jeometry;
import org.jeometry.math.Matrix;
import org.jeometry.math.Vector;

/**
 * This interface describes a linear system solver using matrices. 
 * Let A a general matrix and B a column matrix with the same number of columns as A. 
 * Solving a linear system consists in the determination of the matrix X that is such that:

 * 

 * A×X = B
 * 

 * @author Julien Seinturier - COMEX S.A. - [email protected] - https://github.com/jorigin/jeometry
 * @version {@value Jeometry#version} b{@value Jeometry#BUILD}
 * @since 1.0.0
 */
public interface Solver {

	/**
	 * Identifies a linear solver that uses Gauss elimination. 
	 */
	public static int METHOD_GAUSS    = 1;
	
	/**
	 * Identifies a linear solver that uses LU decomposition.
	 */
	public static int METHOD_LU       = 2;
	
	/**
	 * Identifies a linear solver that uses QR decomposition.
	 */
	public static int METHOD_QR       = 3;	
	
	/**
	 * Identifies a linear solver that uses Cholesky decomposition.
	 */
	public static int METHOD_CHOLESKY = 4;
	
	/**
	 * Return the method used by the solver.
	 * @return the method used by the solver
	 * @see #METHOD_GAUSS
	 * @see #METHOD_LU
	 * @see #METHOD_QR
	 */
	public int getMethod();
	
	/**
	 * Solve the system defined by a×x = b.
	 * @param a the a matrix that contains the coefficients
	 * @param b the b matrix that contains the constants
	 * @return the x matrix that contains the solution or null if no solution has been found
	 * @throws IllegalArgumentException if the input matrices cannot lead to a solution (singular, non invertible, ...)
	 */
	public Matrix solve(Matrix a, Matrix b);
	
	/**
	 * Solve the system defined by a×x = b.
	 * @param a the a matrix that contains the coefficients
	 * @param b the b matrix that contains the constants
	 * @param x the x matrix that contains the solution
	 * @return the same reference as x or null if no solution has been found
	 * @throws IllegalArgumentException if the input matrices cannot lead to a solution (singular, non invertible, ...)
	 */
	public Matrix solve(Matrix a, Matrix b, Matrix x);
	
	/**
	 * Solve the system defined by a×x = b.
	 * @param a the a matrix that contains the coefficients
	 * @param b the b vector that contains the constants
	 * @return the x vector that contains the solution or null if no solution has been found
	 * @throws IllegalArgumentException if the input matrices cannot lead to a solution (singular, non invertible, ...)
	 */
	public Vector solve(Matrix a, Vector b);
	
	/**
	 * Solve the system defined by a×x = b.
	 * @param a the  matrix that contains the coefficients
	 * @param b  the vector that contains the constants
	 * @param x the vector that contains the solution
	 * @return a reference on x or null if no solution has been found
	 * @throws IllegalArgumentException if the input matrices cannot lead to a solution (singular, non invertible, ...)
	 */
	public Vector solve(Matrix a, Vector b, Vector x);
}