nag_superlu_matrix_norm (f11mlc) (PDF version)
f11 Chapter Contents
f11 Chapter Introduction
NAG C Library Manual

NAG Library Function Document

nag_superlu_matrix_norm (f11mlc)

+ Contents

    1  Purpose
    7  Accuracy

1  Purpose

nag_superlu_matrix_norm (f11mlc) computes the 1-norm, the -norm or the maximum absolute value of the elements of a real, square, sparse matrix which is held in compressed column (Harwell–Boeing) format.

2  Specification

#include <nag.h>
#include <nagf11.h>
void  nag_superlu_matrix_norm (Nag_NormType norm, double *anorm, Integer n, const Integer icolzp[], const Integer irowix[], const double a[], NagError *fail)

3  Description

nag_superlu_matrix_norm (f11mlc) computes various quantities relating to norms of a real, sparse n by n matrix A presented in compressed column (Harwell–Boeing) format.

4  References

None.

5  Arguments

1:     normNag_NormTypeInput
On entry: specifies the value to be returned in anorm.
norm=Nag_RealOneNorm
The 1-norm A1 of the matrix is computed, that is max1jni=1nAij.
norm=Nag_RealInfNorm
The -norm A of the matrix is computed, that is max1in j=1n Aij.
norm=Nag_RealMaxNorm
The value max1i,jnAij  (not a norm).
Constraint: norm=Nag_RealOneNorm, Nag_RealInfNorm or Nag_RealMaxNorm.
2:     anormdouble *Output
On exit: the computed quantity relating the matrix.
3:     nIntegerInput
On entry: n, the order of the matrix A.
Constraint: n0.
4:     icolzp[dim]const IntegerInput
Note: the dimension, dim, of the array icolzp must be at least n+1.
On entry: icolzp[i-1] contains the index in A of the start of a new column. See Section 2.1.3 in the f11 Chapter Introduction.
5:     irowix[dim]const IntegerInput
Note: the dimension, dim, of the array irowix must be at least icolzp[n]-1, the number of nonzeros of the sparse matrix A.
On entry: the row index array of the sparse matrix A.
6:     a[dim]const doubleInput
Note: the dimension, dim, of the array a must be at least icolzp[n]-1, the number of nonzeros of the sparse matrix A.
On entry: the array of nonzero values in the sparse matrix A.
7:     failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
NE_BAD_PARAM
On entry, argument number value had an illegal value.
On entry, argument value had an illegal value.
NE_INT
On entry, n=value.
Constraint: n0.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

This example computes norms and maximum absolute value of the matrix A, where
A= 2.00 1.00 0 0 0 0 0 1.00 -1.00 0 4.00 0 1.00 0 1.00 0 0 0 1.00 2.00 0 -2.00 0 0 3.00 .

9.1  Program Text

Program Text (f11mlce.c)

9.2  Program Data

Program Data (f11mlce.d)

9.3  Program Results

Program Results (f11mlce.r)


nag_superlu_matrix_norm (f11mlc) (PDF version)
f11 Chapter Contents
f11 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012