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Fast double-precision vector and matrix maths library for Java, supporting N-dimensional numeric arrays.

There is a newer version: 0.67.0

package mikera.matrixx.impl;

import java.util.Arrays;

import mikera.matrixx.AMatrix;
import mikera.vectorz.AVector;
import mikera.vectorz.Vectorz;
import mikera.vectorz.impl.ArraySubVector;
import mikera.vectorz.impl.IndexedArrayVector;

/**
 * Class for a lower triangular matrix packed densely by rows.
 * 
 * Mutable only in the lower triangular elements
 * 
 * Mostly useful for space efficiency when storing triangular matrices, but is also optimised
 * for certain common operations on triangular matrices.
 * 
 * @author Mike
 *
 */
public final class LowerTriangularMatrix extends ATriangularMatrix implements IFastRows {
	private static final long serialVersionUID = 8413148328738646551L;

	private LowerTriangularMatrix(double[] data, int rows, int cols) {
		super(data, rows, cols);
	}
	
	private LowerTriangularMatrix(int rows, int cols) {
		this (new double[(rows*(rows+1))>>1],rows,cols);
	}
	
	static LowerTriangularMatrix wrap(double[] data, int rows, int cols) {
		return new LowerTriangularMatrix(data,rows,cols);
	}
	
	public static LowerTriangularMatrix createFrom(AMatrix m) {
		int rc=m.rowCount();
		int cc=m.columnCount();
		LowerTriangularMatrix r = new LowerTriangularMatrix(rc,cc);
		for (int j=0; j0)) return Vectorz.createZeroVector(bandLength(band));

		int[] ixs=new int[n];
		for (int i=0; i=j) return internalIndex(i,j);
		throw new IndexOutOfBoundsException("Can't compute array index for sparse entry!");
	}
	
	private int internalIndex(int i, int j) {
		return j + ((i*(i+1))>>1);
	}

	@Override
	public double get(int i, int j) {
		checkIndex(i,j);
		if (j>i) return 0.0;
		return data[internalIndex(i,j)];
	}
	
	@Override
	public double unsafeGet(int i, int j) {
		if (j>i) return 0.0;
		return data[internalIndex(i,j)];
	}
	
	@Override
	public void unsafeSet(int i, int j, double value) {
		data[internalIndex(i,j)]=value;
	}
	
	@Override
	public AVector getRowView(int i) {
		this.checkRow(i);
		int end=Math.min(i+1, cols);
		return ArraySubVector.wrap(data, internalIndex(i,0), end).join(Vectorz.createZeroVector(cols-end));
	}
	
	@Override
	public void copyRowTo(int i, double[] dest, int offset) {
		this.checkRow(i);
		int nn=Math.min(i+1,cols);
		System.arraycopy(data, internalIndex(i,0), dest, offset, nn);
		if (nn