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/* slansy.f -- translated by f2c (version 20061008).
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You must link the resulting object file with libf2c:
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on Microsoft Windows system, link with libf2c.lib;
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm
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or, if you install libf2c.a in a standard place, with -lf2c -lm
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-- in that order, at the end of the command line, as in
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cc *.o -lf2c -lm
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
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http://www.netlib.org/f2c/libf2c.zip
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*/
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#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 slansy_(char *norm, char *uplo, integer *n, real *a, integer *lda,
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real *work)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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real ret_val, r__1, r__2, r__3;
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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__, j;
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real sum, absa, scale;
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extern logical lsame_(char *, char *);
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real value;
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extern /* Subroutine */ int slassq_(integer *, real *, integer *, real *,
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real *);
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/* -- LAPACK auxiliary routine (version 3.2) -- */
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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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/* SLANSY 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 matrix A. */
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/* Description */
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/* =========== */
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/* SLANSY returns the value */
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/* SLANSY = ( 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 SLANSY as described */
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/* above. */
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/* UPLO (input) CHARACTER*1 */
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/* Specifies whether the upper or lower triangular part of the */
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/* symmetric matrix A is to be referenced. */
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/* = 'U': Upper triangular part of A is referenced */
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/* = 'L': Lower triangular part of A is referenced */
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/* N (input) INTEGER */
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/* The order of the matrix A. N >= 0. When N = 0, SLANSY is */
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/* set to zero. */
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/* A (input) REAL array, dimension (LDA,N) */
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/* The symmetric matrix A. If UPLO = 'U', the leading n by n */
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/* upper triangular part of A contains the upper triangular part */
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/* of the matrix A, and the strictly lower triangular part of A */
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/* is not referenced. If UPLO = 'L', the leading n by n lower */
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/* triangular part of A contains the lower triangular part of */
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/* the matrix A, and the strictly upper triangular part of A is */
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/* not referenced. */
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/* LDA (input) INTEGER */
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/* The leading dimension of the array A. LDA >= max(N,1). */
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/* WORK (workspace) REAL array, dimension (MAX(1,LWORK)), */
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/* where LWORK >= N when NORM = 'I' or '1' or 'O'; otherwise, */
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/* WORK is not referenced. */
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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 Subroutines .. */
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/* .. */
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/* .. External Functions .. */
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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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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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a -= a_offset;
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--work;
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/* Function Body */
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if (*n == 0) {
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value = 0.f;
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} else if (lsame_(norm, "M")) {
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/* Find max(abs(A(i,j))). */
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value = 0.f;
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if (lsame_(uplo, "U")) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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i__2 = j;
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for (i__ = 1; i__ <= i__2; ++i__) {
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/* Computing MAX */
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r__2 = value, r__3 = (r__1 = a[i__ + j * a_dim1], dabs(
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r__1));
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value = dmax(r__2,r__3);
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/* L10: */
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}
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/* L20: */
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}
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} else {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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i__2 = *n;
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for (i__ = j; i__ <= i__2; ++i__) {
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/* Computing MAX */
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r__2 = value, r__3 = (r__1 = a[i__ + j * a_dim1], dabs(
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r__1));
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value = dmax(r__2,r__3);
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/* L30: */
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}
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/* L40: */
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}
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}
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} else if (lsame_(norm, "I") || lsame_(norm, "O") || *(unsigned char *)norm == '1') {
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/* Find normI(A) ( = norm1(A), since A is symmetric). */
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value = 0.f;
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if (lsame_(uplo, "U")) {
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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sum = 0.f;
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i__2 = j - 1;
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for (i__ = 1; i__ <= i__2; ++i__) {
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absa = (r__1 = a[i__ + j * a_dim1], dabs(r__1));
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sum += absa;
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work[i__] += absa;
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/* L50: */
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}
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work[j] = sum + (r__1 = a[j + j * a_dim1], dabs(r__1));
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/* L60: */
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}
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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/* Computing MAX */
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r__1 = value, r__2 = work[i__];
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value = dmax(r__1,r__2);
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/* L70: */
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}
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} else {
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i__1 = *n;
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for (i__ = 1; i__ <= i__1; ++i__) {
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work[i__] = 0.f;
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/* L80: */
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}
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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sum = work[j] + (r__1 = a[j + j * a_dim1], dabs(r__1));
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i__2 = *n;
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for (i__ = j + 1; i__ <= i__2; ++i__) {
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absa = (r__1 = a[i__ + j * a_dim1], dabs(r__1));
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sum += absa;
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work[i__] += absa;
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/* L90: */
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}
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value = dmax(value,sum);
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/* L100: */
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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.f;
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sum = 1.f;
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if (lsame_(uplo, "U")) {
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i__1 = *n;
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for (j = 2; j <= i__1; ++j) {
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i__2 = j - 1;
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slassq_(&i__2, &a[j * a_dim1 + 1], &c__1, &scale, &sum);
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/* L110: */
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}
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} else {
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i__1 = *n - 1;
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for (j = 1; j <= i__1; ++j) {
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i__2 = *n - j;
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slassq_(&i__2, &a[j + 1 + j * a_dim1], &c__1, &scale, &sum);
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/* L120: */
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}
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}
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sum *= 2;
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i__1 = *lda + 1;
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slassq_(n, &a[a_offset], &i__1, &scale, &sum);
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value = scale * sqrt(sum);
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}
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ret_val = value;
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return ret_val;
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/* End of SLANSY */
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} /* slansy_ */
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