no.uib.cipr.matrix.AbstractBandMatrix Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of mtj Show documentation
Show all versions of mtj Show documentation
A comprehensive collection of matrix data structures, linear solvers, least squares methods,
eigenvalue, and singular value decompositions.
/*
* Copyright (C) 2003-2006 Bjørn-Ove Heimsund
*
* This file is part of MTJ.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the
* Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package no.uib.cipr.matrix;
import java.util.Arrays;
import java.util.Iterator;
/**
* Partial implementation of a banded matrix
*/
abstract class AbstractBandMatrix extends AbstractMatrix {
/**
* Matrix data
*/
double[] data;
/**
* Number of upper and lower diagonals
*/
int kl, ku;
/**
* Size of the matrix. It is always square
*/
int n;
/**
* Constructor for AbstractBandMatrix
*
* @param n
* Size of the matrix. Since the matrix must be square, this
* equals both the number of rows and columns
* @param kl
* Number of diagonals below the main diagonal
* @param ku
* Number of diagonals above the main diagonal
*/
public AbstractBandMatrix(int n, int kl, int ku) {
super(n, n);
this.n = n;
if (kl < 0 || ku < 0)
throw new IllegalArgumentException("kl < 0 || ku < 0");
this.kl = kl;
this.ku = ku;
data = new double[numColumns * (1 + kl + ku)];
}
/**
* Constructor for AbstractBandMatrix
*
* @param A
* Matrix to copy from
* @param kl
* Number of diagonals below the main diagonal
* @param ku
* Number of diagonals above the main diagonal
*/
public AbstractBandMatrix(Matrix A, int kl, int ku) {
this(A, kl, ku, true);
}
/**
* Constructor for AbstractBandMatrix
*
* @param A
* Matrix to copy from
* @param kl
* Number of diagonals below the main diagonal
* @param ku
* Number of diagonals above the main diagonal
* @param deep
* True if a deep copy is made. For a shallow copy,
* A must be a banded matrix
*/
public AbstractBandMatrix(Matrix A, int kl, int ku, boolean deep) {
super(A);
if (kl < 0 || ku < 0)
throw new IllegalArgumentException("kl < 0 || ku < 0");
if (!isSquare())
throw new IllegalArgumentException("Band matrix must be square");
this.n = numRows;
this.kl = kl;
this.ku = ku;
if (deep) {
data = new double[numColumns * (1 + kl + ku)];
copy(A);
} else
this.data = ((AbstractBandMatrix) A).getData();
}
/**
* Returns the matrix contents
*/
public double[] getData() {
return data;
}
@Override
public void add(int row, int column, double value) {
checkBand(row, column);
data[getIndex(row, column)] += value;
}
@Override
public void set(int row, int column, double value) {
checkBand(row, column);
data[getIndex(row, column)] = value;
}
@Override
public double get(int row, int column) {
if (!inBand(row, column))
return 0;
return data[getIndex(row, column)];
}
/**
* Returns the number of lower diagonals
*/
public int numSubDiagonals() {
return kl;
}
/**
* Returns the number of upper diagonals
*/
public int numSuperDiagonals() {
return ku;
}
/**
* Returns true if the given indices are within the band
*/
boolean inBand(int row, int column) {
return column - ku <= row && row <= column + kl;
}
/**
* Checks that the indices are within the band
*/
void checkBand(int row, int column) {
if (!inBand(row, column))
throw new IndexOutOfBoundsException("Insertion index out of band");
}
/**
* Checks the row and column indices, and returns the linear data index
*/
int getIndex(int row, int column) {
check(row, column);
return ku + row - column + column * (kl + ku + 1);
}
/**
* Set this matrix equal to the given matrix
*/
void copy(Matrix A) {
for (MatrixEntry e : A)
if (inBand(e.row(), e.column()))
set(e.row(), e.column(), e.get());
}
@Override
public Matrix set(Matrix B) {
if (!(B instanceof AbstractBandMatrix))
return super.set(B);
checkSize(B);
AbstractBandMatrix Bb = (AbstractBandMatrix) B;
if (Bb.kl != kl)
throw new IllegalArgumentException("B.kl != kl");
if (Bb.ku != ku)
throw new IllegalArgumentException("B.ku != ku");
double[] Bd = Bb.getData();
if (Bd == data)
return this;
System.arraycopy(Bd, 0, data, 0, data.length);
return this;
}
@Override
public Matrix zero() {
Arrays.fill(data, 0);
return this;
}
@Override
public Iterator iterator() {
return new BandMatrixIterator();
}
/**
* Iterator over a band matrix
*/
class BandMatrixIterator extends RefMatrixIterator {
/**
* Matrix bandwidths. Cannot be taken directly from the matrix since
* that breaks iterating over symmetrical matrices
*/
private final int lkl, lku;
public BandMatrixIterator(int lkl, int lku) {
this.lkl = lkl;
this.lku = lku;
}
public BandMatrixIterator() {
this(kl, ku);
}
@Override
public MatrixEntry next() {
entry.update(row, column);
// Traversal first down the columns, then the rows
if (row < Math.min(column + lkl, n - 1)
&& row >= Math.max(column - lku, 0))
row++;
else {
column++;
row = Math.max(column - lku, 0);
}
return entry;
}
}
}