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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;
/**
* Lower triangular packed matrix. In contrast with
* {@link no.uib.cipr.matrix.LowerTriangDenseMatrix LowerTriangDenseMatrix},
* this matrix exploits the sparsity by only storing about half the matrix. As
* such, the triangular matrix
*
*
*
* a11
*
*
*
*
*
* a21
* a22
*
*
*
*
* a31
* a32
* a33
*
*
*
* a41
* a42
* a43
* a44
*
*
*
*
* is packed as follows:
*
*
*
*
* a11
* a21
* a31
* a41
* a22
* a32
* a42
* a33
* a43
* a44
*
*
*
*/
public class LowerTriangPackMatrix extends AbstractTriangPackMatrix {
/**
* Constructor for LowerTriangPackMatrix
*
* @param n
* Size of the matrix. Since the matrix must be square, this
* equals both the number of rows and columns
*/
public LowerTriangPackMatrix(int n) {
super(n, UpLo.Lower, Diag.NonUnit);
}
/**
* Constructor for LowerTriangPackMatrix
*
* @param n
* Size of the matrix. Since the matrix must be square, this
* equals both the number of rows and columns
*/
LowerTriangPackMatrix(int n, Diag diag) {
super(n, UpLo.Lower, diag);
}
/**
* Constructor for LowerTriangPackMatrix
*
* @param A
* Matrix to copy contents from. Only the entries of the relevant
* part are copied
*/
public LowerTriangPackMatrix(Matrix A) {
this(A, true);
}
/**
* Constructor for LowerTriangPackMatrix
*
* @param A
* Matrix to copy contents from. Only the entries of the relevant
* part are copied
* @param deep
* True if the copy is deep, else false (giving a shallow copy).
* For shallow copies, A must be a packed matrix
*/
public LowerTriangPackMatrix(Matrix A, boolean deep) {
super(A, deep, UpLo.Lower, Diag.NonUnit);
}
/**
* Constructor for LowerTriangPackMatrix
*
* @param A
* Matrix to copy contents from. Only the entries of the relevant
* part are copied
* @param deep
* True if the copy is deep, else false (giving a shallow copy).
* For shallow copies, A must be a packed matrix
*/
LowerTriangPackMatrix(Matrix A, boolean deep, Diag diag) {
super(A, deep, UpLo.Lower, diag);
}
@Override
public void add(int row, int column, double value) {
if (column > row)
throw new IllegalArgumentException("column > row");
data[getIndex(row, column)] += value;
}
@Override
public void set(int row, int column, double value) {
if (column > row)
throw new IllegalArgumentException("column > row");
data[getIndex(row, column)] = value;
}
@Override
public double get(int row, int column) {
if (column > row)
return 0;
return data[getIndex(row, column)];
}
/**
* Checks the row and column indices, and returns the linear data index
*/
int getIndex(int row, int column) {
check(row, column);
return row + (2 * n - (column + 1)) * column / 2;
}
@Override
void copy(Matrix A) {
for (MatrixEntry e : A)
if (e.row() >= e.column())
set(e.row(), e.column(), e.get());
}
@Override
public LowerTriangPackMatrix copy() {
return new LowerTriangPackMatrix(this);
}
}