/* -- translated by f2c (version 20100827).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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*/
#include "f2c.h"
/* Table of constant values */
static integer c__1 = 1;
/* > \brief \b DLANST returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the ele
ment of largest absolute value of a real symmetric tridiagonal matrix.
=========== DOCUMENTATION ===========
Online html documentation available at
http://www.netlib.org/lapack/explore-html/
> \htmlonly
> Download DLANST + dependencies
> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlanst.
f">
> [TGZ]</a>
> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlanst.
f">
> [ZIP]</a>
> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlanst.
f">
> [TXT]</a>
> \endhtmlonly
Definition:
===========
DOUBLE PRECISION FUNCTION DLANST( NORM, N, D, E )
CHARACTER NORM
INTEGER N
DOUBLE PRECISION D( * ), E( * )
> \par Purpose:
=============
>
> \verbatim
>
> DLANST returns the value of the one norm, or the Frobenius norm, or
> the infinity norm, or the element of largest absolute value of a
> real symmetric tridiagonal matrix A.
> \endverbatim
>
> \return DLANST
> \verbatim
>
> DLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm'
> (
> ( norm1(A), NORM = '1', 'O' or 'o'
> (
> ( normI(A), NORM = 'I' or 'i'
> (
> ( normF(A), NORM = 'F', 'f', 'E' or 'e'
>
> where norm1 denotes the one norm of a matrix (maximum column sum),
> normI denotes the infinity norm of a matrix (maximum row sum) and
> normF denotes the Frobenius norm of a matrix (square root of sum of
> squares). Note that max(abs(A(i,j))) is not a consistent matrix norm.
> \endverbatim
Arguments:
==========
> \param[in] NORM
> \verbatim
> NORM is CHARACTER*1
> Specifies the value to be returned in DLANST as described
> above.
> \endverbatim
>
> \param[in] N
> \verbatim
> N is INTEGER
> The order of the matrix A. N >= 0. When N = 0, DLANST is
> set to zero.
> \endverbatim
>
> \param[in] D
> \verbatim
> D is DOUBLE PRECISION array, dimension (N)
> The diagonal elements of A.
> \endverbatim
>
> \param[in] E
> \verbatim
> E is DOUBLE PRECISION array, dimension (N-1)
> The (n-1) sub-diagonal or super-diagonal elements of A.
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date September 2012
> \ingroup auxOTHERauxiliary
===================================================================== */
doublereal igraphdlanst_(char *norm, integer *n, doublereal *d__, doublereal *e)
{
/* System generated locals */
integer i__1;
doublereal ret_val, d__1, d__2, d__3;
/* Builtin functions */
double sqrt(doublereal);
/* Local variables */
integer i__;
doublereal sum, scale;
extern logical igraphlsame_(char *, char *);
doublereal anorm = 0.;
extern logical igraphdisnan_(doublereal *);
extern /* Subroutine */ int igraphdlassq_(integer *, doublereal *, integer *,
doublereal *, doublereal *);
/* -- LAPACK auxiliary routine (version 3.4.2) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
September 2012
=====================================================================
Parameter adjustments */
--e;
--d__;
/* Function Body */
if (*n <= 0) {
anorm = 0.;
} else if (igraphlsame_(norm, "M")) {
/* Find max(abs(A(i,j))). */
anorm = (d__1 = d__[*n], abs(d__1));
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
sum = (d__1 = d__[i__], abs(d__1));
if (anorm < sum || igraphdisnan_(&sum)) {
anorm = sum;
}
sum = (d__1 = e[i__], abs(d__1));
if (anorm < sum || igraphdisnan_(&sum)) {
anorm = sum;
}
/* L10: */
}
} else if (igraphlsame_(norm, "O") || *(unsigned char *)
norm == '1' || igraphlsame_(norm, "I")) {
/* Find norm1(A). */
if (*n == 1) {
anorm = abs(d__[1]);
} else {
anorm = abs(d__[1]) + abs(e[1]);
sum = (d__1 = e[*n - 1], abs(d__1)) + (d__2 = d__[*n], abs(d__2));
if (anorm < sum || igraphdisnan_(&sum)) {
anorm = sum;
}
i__1 = *n - 1;
for (i__ = 2; i__ <= i__1; ++i__) {
sum = (d__1 = d__[i__], abs(d__1)) + (d__2 = e[i__], abs(d__2)
) + (d__3 = e[i__ - 1], abs(d__3));
if (anorm < sum || igraphdisnan_(&sum)) {
anorm = sum;
}
/* L20: */
}
}
} else if (igraphlsame_(norm, "F") || igraphlsame_(norm, "E")) {
/* Find normF(A). */
scale = 0.;
sum = 1.;
if (*n > 1) {
i__1 = *n - 1;
igraphdlassq_(&i__1, &e[1], &c__1, &scale, &sum);
sum *= 2;
}
igraphdlassq_(n, &d__[1], &c__1, &scale, &sum);
anorm = scale * sqrt(sum);
}
ret_val = anorm;
return ret_val;
/* End of DLANST */
} /* igraphdlanst_ */