/* sspmv.f -- translated by f2c (version 20100827).
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 "datatypes.h"
/* Subroutine */ int sspmv_(char *uplo, integer *n, real *alpha, real *ap,
real *x, integer *incx, real *beta, real *y, integer *incy, ftnlen
uplo_len)
{
/* System generated locals */
integer i__1, i__2;
/* Local variables */
integer i__, j, k, kk, ix, iy, jx, jy, kx, ky, info;
real temp1, temp2;
extern logical lsame_(char *, char *, ftnlen, ftnlen);
extern /* Subroutine */ int xerbla_(char *, integer *, ftnlen);
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SSPMV performs the matrix-vector operation */
/* y := alpha*A*x + beta*y, */
/* where alpha and beta are scalars, x and y are n element vectors 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 - REAL . */
/* On entry, ALPHA specifies the scalar alpha. */
/* Unchanged on exit. */
/* AP - REAL 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. */
/* 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. */
/* Unchanged on exit. */
/* X - REAL 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. */
/* BETA - REAL . */
/* On entry, BETA specifies the scalar beta. When BETA is */
/* supplied as zero then Y need not be set on input. */
/* Unchanged on exit. */
/* Y - REAL array of dimension at least */
/* ( 1 + ( n - 1 )*abs( INCY ) ). */
/* Before entry, the incremented array Y must contain the n */
/* element vector y. On exit, Y is overwritten by the updated */
/* vector y. */
/* INCY - INTEGER. */
/* On entry, INCY specifies the increment for the elements of */
/* Y. INCY must not be zero. */
/* Unchanged on exit. */
/* Further Details */
/* =============== */
/* 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 */
--y;
--x;
--ap;
/* Function Body */
info = 0;
if (! lsame_(uplo, "U", (ftnlen)1, (ftnlen)1) && ! lsame_(uplo, "L", (
ftnlen)1, (ftnlen)1)) {
info = 1;
} else if (*n < 0) {
info = 2;
} else if (*incx == 0) {
info = 6;
} else if (*incy == 0) {
info = 9;
}
if (info != 0) {
xerbla_("SSPMV ", &info, (ftnlen)6);
return 0;
}
/* Quick return if possible. */
if (*n == 0 || (*alpha == 0.f && *beta == 1.f)) {
return 0;
}
/* Set up the start points in X and Y. */
if (*incx > 0) {
kx = 1;
} else {
kx = 1 - (*n - 1) * *incx;
}
if (*incy > 0) {
ky = 1;
} else {
ky = 1 - (*n - 1) * *incy;
}
/* Start the operations. In this version the elements of the array AP */
/* are accessed sequentially with one pass through AP. */
/* First form y := beta*y. */
if (*beta != 1.f) {
if (*incy == 1) {
if (*beta == 0.f) {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
y[i__] = 0.f;
/* L10: */
}
} else {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
y[i__] = *beta * y[i__];
/* L20: */
}
}
} else {
iy = ky;
if (*beta == 0.f) {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
y[iy] = 0.f;
iy += *incy;
/* L30: */
}
} else {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
y[iy] = *beta * y[iy];
iy += *incy;
/* L40: */
}
}
}
}
if (*alpha == 0.f) {
return 0;
}
kk = 1;
if (lsame_(uplo, "U", (ftnlen)1, (ftnlen)1)) {
/* Form y when AP contains the upper triangle. */
if (*incx == 1 && *incy == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
temp1 = *alpha * x[j];
temp2 = 0.f;
k = kk;
i__2 = j - 1;
for (i__ = 1; i__ <= i__2; ++i__) {
y[i__] += temp1 * ap[k];
temp2 += ap[k] * x[i__];
++k;
/* L50: */
}
y[j] = y[j] + temp1 * ap[kk + j - 1] + *alpha * temp2;
kk += j;
/* L60: */
}
} else {
jx = kx;
jy = ky;
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
temp1 = *alpha * x[jx];
temp2 = 0.f;
ix = kx;
iy = ky;
i__2 = kk + j - 2;
for (k = kk; k <= i__2; ++k) {
y[iy] += temp1 * ap[k];
temp2 += ap[k] * x[ix];
ix += *incx;
iy += *incy;
/* L70: */
}
y[jy] = y[jy] + temp1 * ap[kk + j - 1] + *alpha * temp2;
jx += *incx;
jy += *incy;
kk += j;
/* L80: */
}
}
} else {
/* Form y when AP contains the lower triangle. */
if (*incx == 1 && *incy == 1) {
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
temp1 = *alpha * x[j];
temp2 = 0.f;
y[j] += temp1 * ap[kk];
k = kk + 1;
i__2 = *n;
for (i__ = j + 1; i__ <= i__2; ++i__) {
y[i__] += temp1 * ap[k];
temp2 += ap[k] * x[i__];
++k;
/* L90: */
}
y[j] += *alpha * temp2;
kk += *n - j + 1;
/* L100: */
}
} else {
jx = kx;
jy = ky;
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
temp1 = *alpha * x[jx];
temp2 = 0.f;
y[jy] += temp1 * ap[kk];
ix = jx;
iy = jy;
i__2 = kk + *n - j;
for (k = kk + 1; k <= i__2; ++k) {
ix += *incx;
iy += *incy;
y[iy] += temp1 * ap[k];
temp2 += ap[k] * x[ix];
/* L110: */
}
y[jy] += *alpha * temp2;
jx += *incx;
jy += *incy;
kk += *n - j + 1;
/* L120: */
}
}
}
return 0;
/* End of SSPMV . */
} /* sspmv_ */