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/* zlangt.f -- translated by f2c (version 20061008).
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.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
doublereal zlangt_(char *norm, integer *n, doublecomplex *dl, doublecomplex *
d__, doublecomplex *du)
{
/* System generated locals */
integer i__1;
doublereal ret_val, d__1, d__2;
/* Builtin functions */
double z_abs(doublecomplex *), sqrt(doublereal);
/* Local variables */
integer i__;
doublereal sum, scale;
extern logical lsame_(char *, char *);
doublereal anorm;
extern /* Subroutine */ int zlassq_(integer *, doublecomplex *, integer *,
doublereal *, doublereal *);
/* -- LAPACK auxiliary routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* ZLANGT returns the value of the one norm, or the Frobenius norm, or */
/* the infinity norm, or the element of largest absolute value of a */
/* complex tridiagonal matrix A. */
/* Description */
/* =========== */
/* ZLANGT returns the value */
/* ZLANGT = ( 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. */
/* Arguments */
/* ========= */
/* NORM (input) CHARACTER*1 */
/* Specifies the value to be returned in ZLANGT as described */
/* above. */
/* N (input) INTEGER */
/* The order of the matrix A. N >= 0. When N = 0, ZLANGT is */
/* set to zero. */
/* DL (input) COMPLEX*16 array, dimension (N-1) */
/* The (n-1) sub-diagonal elements of A. */
/* D (input) COMPLEX*16 array, dimension (N) */
/* The diagonal elements of A. */
/* DU (input) COMPLEX*16 array, dimension (N-1) */
/* The (n-1) super-diagonal elements of A. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
--du;
--d__;
--dl;
/* Function Body */
if (*n <= 0) {
anorm = 0.;
} else if (lsame_(norm, "M")) {
/* Find max(abs(A(i,j))). */
anorm = z_abs(&d__[*n]);
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Computing MAX */
d__1 = anorm, d__2 = z_abs(&dl[i__]);
anorm = max(d__1,d__2);
/* Computing MAX */
d__1 = anorm, d__2 = z_abs(&d__[i__]);
anorm = max(d__1,d__2);
/* Computing MAX */
d__1 = anorm, d__2 = z_abs(&du[i__]);
anorm = max(d__1,d__2);
/* L10: */
}
} else if (lsame_(norm, "O") || *(unsigned char *)
norm == '1') {
/* Find norm1(A). */
if (*n == 1) {
anorm = z_abs(&d__[1]);
} else {
/* Computing MAX */
d__1 = z_abs(&d__[1]) + z_abs(&dl[1]), d__2 = z_abs(&d__[*n]) +
z_abs(&du[*n - 1]);
anorm = max(d__1,d__2);
i__1 = *n - 1;
for (i__ = 2; i__ <= i__1; ++i__) {
/* Computing MAX */
d__1 = anorm, d__2 = z_abs(&d__[i__]) + z_abs(&dl[i__]) +
z_abs(&du[i__ - 1]);
anorm = max(d__1,d__2);
/* L20: */
}
}
} else if (lsame_(norm, "I")) {
/* Find normI(A). */
if (*n == 1) {
anorm = z_abs(&d__[1]);
} else {
/* Computing MAX */
d__1 = z_abs(&d__[1]) + z_abs(&du[1]), d__2 = z_abs(&d__[*n]) +
z_abs(&dl[*n - 1]);
anorm = max(d__1,d__2);
i__1 = *n - 1;
for (i__ = 2; i__ <= i__1; ++i__) {
/* Computing MAX */
d__1 = anorm, d__2 = z_abs(&d__[i__]) + z_abs(&du[i__]) +
z_abs(&dl[i__ - 1]);
anorm = max(d__1,d__2);
/* L30: */
}
}
} else if (lsame_(norm, "F") || lsame_(norm, "E")) {
/* Find normF(A). */
scale = 0.;
sum = 1.;
zlassq_(n, &d__[1], &c__1, &scale, &sum);
if (*n > 1) {
i__1 = *n - 1;
zlassq_(&i__1, &dl[1], &c__1, &scale, &sum);
i__1 = *n - 1;
zlassq_(&i__1, &du[1], &c__1, &scale, &sum);
}
anorm = scale * sqrt(sum);
}
ret_val = anorm;
return ret_val;
/* End of ZLANGT */
} /* zlangt_ */
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