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154 lines
4.0 KiB
C
154 lines
4.0 KiB
C
#include "clapack.h"
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/* Table of constant values */
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static integer c__1 = 1;
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doublereal dlanst_(char *norm, integer *n, doublereal *d__, doublereal *e)
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{
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/* System generated locals */
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integer i__1;
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doublereal ret_val, d__1, d__2, d__3, d__4, d__5;
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/* Builtin functions */
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double sqrt(doublereal);
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/* Local variables */
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integer i__;
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doublereal sum, scale;
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extern logical lsame_(char *, char *);
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doublereal anorm;
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extern /* Subroutine */ int dlassq_(integer *, doublereal *, integer *,
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doublereal *, doublereal *);
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/* -- LAPACK auxiliary routine (version 3.1) -- */
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
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/* November 2006 */
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* Purpose */
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/* ======= */
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/* DLANST returns the value of the one norm, or the Frobenius norm, or */
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/* the infinity norm, or the element of largest absolute value of a */
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/* real symmetric tridiagonal matrix A. */
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/* Description */
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/* =========== */
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/* DLANST returns the value */
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/* DLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm' */
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/* ( */
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/* ( norm1(A), NORM = '1', 'O' or 'o' */
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/* ( */
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/* ( normI(A), NORM = 'I' or 'i' */
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/* ( */
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/* ( normF(A), NORM = 'F', 'f', 'E' or 'e' */
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/* where norm1 denotes the one norm of a matrix (maximum column sum), */
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/* normI denotes the infinity norm of a matrix (maximum row sum) and */
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/* normF denotes the Frobenius norm of a matrix (square root of sum of */
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/* squares). Note that max(abs(A(i,j))) is not a consistent matrix norm. */
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/* Arguments */
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/* ========= */
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/* NORM (input) CHARACTER*1 */
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/* Specifies the value to be returned in DLANST as described */
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/* above. */
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/* N (input) INTEGER */
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/* The order of the matrix A. N >= 0. When N = 0, DLANST is */
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/* set to zero. */
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/* D (input) DOUBLE PRECISION array, dimension (N) */
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/* The diagonal elements of A. */
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/* E (input) DOUBLE PRECISION array, dimension (N-1) */
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/* The (n-1) sub-diagonal or super-diagonal elements of A. */
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/* ===================================================================== */
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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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/* Parameter adjustments */
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--e;
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--d__;
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/* Function Body */
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if (*n <= 0) {
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anorm = 0.;
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} else if (lsame_(norm, "M")) {
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/* Find max(abs(A(i,j))). */
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anorm = (d__1 = d__[*n], abs(d__1));
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i__1 = *n - 1;
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for (i__ = 1; i__ <= i__1; ++i__) {
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/* Computing MAX */
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d__2 = anorm, d__3 = (d__1 = d__[i__], abs(d__1));
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anorm = max(d__2,d__3);
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/* Computing MAX */
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d__2 = anorm, d__3 = (d__1 = e[i__], abs(d__1));
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anorm = max(d__2,d__3);
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/* L10: */
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}
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} else if (lsame_(norm, "O") || *(unsigned char *)
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norm == '1' || lsame_(norm, "I")) {
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/* Find norm1(A). */
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if (*n == 1) {
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anorm = abs(d__[1]);
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} else {
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/* Computing MAX */
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d__3 = abs(d__[1]) + abs(e[1]), d__4 = (d__1 = e[*n - 1], abs(
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d__1)) + (d__2 = d__[*n], abs(d__2));
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anorm = max(d__3,d__4);
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i__1 = *n - 1;
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for (i__ = 2; i__ <= i__1; ++i__) {
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/* Computing MAX */
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d__4 = anorm, d__5 = (d__1 = d__[i__], abs(d__1)) + (d__2 = e[
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i__], abs(d__2)) + (d__3 = e[i__ - 1], abs(d__3));
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anorm = max(d__4,d__5);
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/* L20: */
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}
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}
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} else if (lsame_(norm, "F") || lsame_(norm, "E")) {
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/* Find normF(A). */
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scale = 0.;
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sum = 1.;
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if (*n > 1) {
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i__1 = *n - 1;
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dlassq_(&i__1, &e[1], &c__1, &scale, &sum);
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sum *= 2;
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}
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dlassq_(n, &d__[1], &c__1, &scale, &sum);
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anorm = scale * sqrt(sum);
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}
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ret_val = anorm;
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return ret_val;
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/* End of DLANST */
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} /* dlanst_ */
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