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/* dspr.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"
/* Subroutine */ int dspr_(char *uplo, integer *n, doublereal *alpha,
doublereal *x, integer *incx, doublereal *ap)
{
/* System generated locals */
integer i__1, i__2;
/* Local variables */
integer i__, j, k, kk, ix, jx, kx, info;
doublereal temp;
extern logical lsame_(char *, char *);
extern /* Subroutine */ int xerbla_(char *, integer *);
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DSPR 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, supplied in packed form. */
/* Arguments */
/* ========== */
/* UPLO - CHARACTER*1. */
/* On entry, UPLO specifies whether the upper or lower */
/* triangular part of the matrix A is supplied in the packed */
/* array AP as follows: */
/* UPLO = 'U' or 'u' The upper triangular part of A is */
/* supplied in AP. */
/* UPLO = 'L' or 'l' The lower triangular part of A is */
/* supplied in AP. */
/* 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. */
/* AP - DOUBLE PRECISION array of DIMENSION at least */
/* ( ( n*( n + 1 ) )/2 ). */
/* Before entry with UPLO = 'U' or 'u', the array AP must */
/* contain the upper triangular part of the symmetric matrix */
/* packed sequentially, column by column, so that AP( 1 ) */
/* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) */
/* and a( 2, 2 ) respectively, and so on. On exit, the array */
/* AP is overwritten by the upper triangular part of the */
/* updated matrix. */
/* Before entry with UPLO = 'L' or 'l', the array AP must */
/* contain the lower triangular part of the symmetric matrix */
/* packed sequentially, column by column, so that AP( 1 ) */
/* contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) */
/* and a( 3, 1 ) respectively, and so on. On exit, the array */
/* AP is overwritten by the lower triangular part of the */
/* updated matrix. */
/* 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 .. */
/* .. */
/* Test the input parameters. */
/* Parameter adjustments */
--ap;
--x;
/* 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;
}
if (info != 0) {
xerbla_("DSPR ", &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 the array AP */
/* are accessed sequentially with one pass through AP. */
kk = 1;
if (lsame_(uplo, "U")) {
/* Form A when upper triangle is stored in AP. */
if (*incx == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[j] != 0.) {
temp = *alpha * x[j];
k = kk;
i__2 = j;
for (i__ = 1; i__ <= i__2; ++i__) {
ap[k] += x[i__] * temp;
++k;
/* L10: */
}
}
kk += j;
/* 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 = kk + j - 1;
for (k = kk; k <= i__2; ++k) {
ap[k] += x[ix] * temp;
ix += *incx;
/* L30: */
}
}
jx += *incx;
kk += j;
/* L40: */
}
}
} else {
/* Form A when lower triangle is stored in AP. */
if (*incx == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
if (x[j] != 0.) {
temp = *alpha * x[j];
k = kk;
i__2 = *n;
for (i__ = j; i__ <= i__2; ++i__) {
ap[k] += x[i__] * temp;
++k;
/* L50: */
}
}
kk = kk + *n - j + 1;
/* 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 = kk + *n - j;
for (k = kk; k <= i__2; ++k) {
ap[k] += x[ix] * temp;
ix += *incx;
/* L70: */
}
}
jx += *incx;
kk = kk + *n - j + 1;
/* L80: */
}
}
}
return 0;
/* End of DSPR . */
} /* dspr_ */
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