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/* dsyr.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 "clapack.h"
/* Subroutine */ int dsyr_(char *uplo, integer *n, doublereal *alpha,
doublereal *x, integer *incx, doublereal *a, integer *lda)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
/* Local variables */
integer i__, j, ix, jx, kx, info;
doublereal temp;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int xerbla_(char *, integer *);
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DSYR performs the symmetric rank 1 operation */
/* A := alpha*x*x' + A, */
/* where alpha is a real scalar, x is an n element vector and A is an */
/* n by n symmetric matrix. */
/* Arguments */
/* ========== */
/* UPLO - CHARACTER*1. */
/* On entry, UPLO specifies whether the upper or lower */
/* triangular part of the array A is to be referenced as */
/* follows: */
/* UPLO = 'U' or 'u' Only the upper triangular part of A */
/* is to be referenced. */
/* UPLO = 'L' or 'l' Only the lower triangular part of A */
/* is to be referenced. */
/* Unchanged on exit. */
/* N - INTEGER. */
/* On entry, N specifies the order of the matrix A. */
/* N must be at least zero. */
/* Unchanged on exit. */
/* ALPHA - DOUBLE PRECISION. */
/* On entry, ALPHA specifies the scalar alpha. */
/* Unchanged on exit. */
/* X - DOUBLE PRECISION array of dimension at least */
/* ( 1 + ( n - 1 )*abs( INCX ) ). */
/* Before entry, the incremented array X must contain the n */
/* element vector x. */
/* Unchanged on exit. */
/* INCX - INTEGER. */
/* On entry, INCX specifies the increment for the elements of */
/* X. INCX must not be zero. */
/* Unchanged on exit. */
/* A - DOUBLE PRECISION array of DIMENSION ( LDA, n ). */
/* Before entry with UPLO = 'U' or 'u', the leading n by n */
/* upper triangular part of the array A must contain the upper */
/* triangular part of the symmetric matrix and the strictly */
/* lower triangular part of A is not referenced. On exit, the */
/* upper triangular part of the array A is overwritten by the */
/* upper triangular part of the updated matrix. */
/* Before entry with UPLO = 'L' or 'l', the leading n by n */
/* lower triangular part of the array A must contain the lower */
/* triangular part of the symmetric matrix and the strictly */
/* upper triangular part of A is not referenced. On exit, the */
/* lower triangular part of the array A is overwritten by the */
/* lower triangular part of the updated matrix. */
/* LDA - INTEGER. */
/* On entry, LDA specifies the first dimension of A as declared */
/* in the calling (sub) program. LDA must be at least */
/* max( 1, n ). */
/* Unchanged on exit. */
/* Level 2 Blas routine. */
/* -- Written on 22-October-1986. */
/* Jack Dongarra, Argonne National Lab. */
/* Jeremy Du Croz, Nag Central Office. */
/* Sven Hammarling, Nag Central Office. */
/* Richard Hanson, Sandia National Labs. */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* Test the input parameters. */
/* Parameter adjustments */
--x;
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
/* Function Body */
info = 0;
if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {
info = 1;
} else if (*n < 0) {
info = 2;
} else if (*incx == 0) {
info = 5;
} else if (*lda < max(1,*n)) {
info = 7;
}
if (info != 0) {
xerbla_("DSYR ", &info);
return 0;
}
/* Quick return if possible. */
if (*n == 0 || *alpha == 0.) {
return 0;
}
/* Set the start point in X if the increment is not unity. */
if (*incx <= 0) {
kx = 1 - (*n - 1) * *incx;
} else if (*incx != 1) {
kx = 1;
}
/* Start the operations. In this version the elements of A are */
/* accessed sequentially with one pass through the triangular part */
/* of A. */
if (lsame_(uplo, "U")) {
/* Form A when A is stored in upper triangle. */
if (*incx == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[j] != 0.) {
temp = *alpha * x[j];
i__2 = j;
for (i__ = 1; i__ <= i__2; ++i__) {
a[i__ + j * a_dim1] += x[i__] * temp;
/* L10: */
}
}
/* L20: */
}
} else {
jx = kx;
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[jx] != 0.) {
temp = *alpha * x[jx];
ix = kx;
i__2 = j;
for (i__ = 1; i__ <= i__2; ++i__) {
a[i__ + j * a_dim1] += x[ix] * temp;
ix += *incx;
/* L30: */
}
}
jx += *incx;
/* L40: */
}
}
} else {
/* Form A when A is stored in lower triangle. */
if (*incx == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[j] != 0.) {
temp = *alpha * x[j];
i__2 = *n;
for (i__ = j; i__ <= i__2; ++i__) {
a[i__ + j * a_dim1] += x[i__] * temp;
/* L50: */
}
}
/* L60: */
}
} else {
jx = kx;
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[jx] != 0.) {
temp = *alpha * x[jx];
ix = jx;
i__2 = *n;
for (i__ = j; i__ <= i__2; ++i__) {
a[i__ + j * a_dim1] += x[ix] * temp;
ix += *incx;
/* L70: */
}
}
jx += *incx;
/* L80: */
}
}
}
return 0;
/* End of DSYR . */
} /* dsyr_ */