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/* dla_syamv.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 dla_syamv__(integer *uplo, integer *n, doublereal *alpha,
doublereal *a, integer *lda, doublereal *x, integer *incx,
doublereal *beta, doublereal *y, integer *incy)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
doublereal d__1;
/* Builtin functions */
double d_sign(doublereal *, doublereal *);
/* Local variables */
integer i__, j;
logical symb_zero__;
integer iy, jx, kx, ky, info;
doublereal temp, safe1;
extern doublereal dlamch_(char *);
extern /* Subroutine */ int xerbla_(char *, integer *);
extern integer ilauplo_(char *);
/* -- LAPACK routine (version 3.2) -- */
/* -- Contributed by James Demmel, Deaglan Halligan, Yozo Hida and -- */
/* -- Jason Riedy of Univ. of California Berkeley. -- */
/* -- November 2008 -- */
/* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
/* -- Univ. of California Berkeley and NAG Ltd. -- */
/* .. */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DLA_SYAMV performs the matrix-vector operation */
/* y := alpha*abs(A)*abs(x) + beta*abs(y), */
/* where alpha and beta are scalars, x and y are vectors and A is an */
/* n by n symmetric matrix. */
/* This function is primarily used in calculating error bounds. */
/* To protect against underflow during evaluation, components in */
/* the resulting vector are perturbed away from zero by (N+1) */
/* times the underflow threshold. To prevent unnecessarily large */
/* errors for block-structure embedded in general matrices, */
/* "symbolically" zero components are not perturbed. A zero */
/* entry is considered "symbolic" if all multiplications involved */
/* in computing that entry have at least one zero multiplicand. */
/* Parameters */
/* ========== */
/* UPLO - INTEGER */
/* On entry, UPLO specifies whether the upper or lower */
/* triangular part of the array A is to be referenced as */
/* follows: */
/* UPLO = BLAS_UPPER Only the upper triangular part of A */
/* is to be referenced. */
/* UPLO = BLAS_LOWER Only the lower triangular part of A */
/* is to be referenced. */
/* Unchanged on exit. */
/* N - INTEGER. */
/* On entry, N specifies the number of columns 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. */
/* A - DOUBLE PRECISION array of DIMENSION ( LDA, n ). */
/* Before entry, the leading m by n part of the array A must */
/* contain the matrix of coefficients. */
/* Unchanged on exit. */
/* 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. */
/* X - DOUBLE PRECISION array of DIMENSION at least */
/* ( 1 + ( n - 1 )*abs( INCX ) ) */
/* Before entry, the incremented array X must contain the */
/* 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 - DOUBLE PRECISION . */
/* 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 - DOUBLE PRECISION array of DIMENSION at least */
/* ( 1 + ( n - 1 )*abs( INCY ) ) */
/* Before entry with BETA non-zero, the incremented array Y */
/* must contain the 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. */
/* 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. */
/* -- Modified for the absolute-value product, April 2006 */
/* Jason Riedy, UC Berkeley */
/* .. */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Test the input parameters. */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--x;
--y;
/* Function Body */
info = 0;
if (*uplo != ilauplo_("U") && *uplo != ilauplo_("L")
) {
info = 1;
} else if (*n < 0) {
info = 2;
} else if (*lda < max(1,*n)) {
info = 5;
} else if (*incx == 0) {
info = 7;
} else if (*incy == 0) {
info = 10;
}
if (info != 0) {
xerbla_("DSYMV ", &info);
return 0;
}
/* Quick return if possible. */
if (*n == 0 || *alpha == 0. && *beta == 1.) {
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;
}
/* Set SAFE1 essentially to be the underflow threshold times the */
/* number of additions in each row. */
safe1 = dlamch_("Safe minimum");
safe1 = (*n + 1) * safe1;
/* Form y := alpha*abs(A)*abs(x) + beta*abs(y). */
/* The O(N^2) SYMB_ZERO tests could be replaced by O(N) queries to */
/* the inexact flag. Still doesn't help change the iteration order */
/* to per-column. */
iy = ky;
if (*incx == 1) {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
if (*beta == 0.) {
symb_zero__ = TRUE_;
y[iy] = 0.;
} else if (y[iy] == 0.) {
symb_zero__ = TRUE_;
} else {
symb_zero__ = FALSE_;
y[iy] = *beta * (d__1 = y[iy], abs(d__1));
}
if (*alpha != 0.) {
i__2 = *n;
for (j = 1; j <= i__2; ++j) {
if (*uplo == ilauplo_("U")) {
if (i__ <= j) {
temp = (d__1 = a[i__ + j * a_dim1], abs(d__1));
} else {
temp = (d__1 = a[j + i__ * a_dim1], abs(d__1));
}
} else {
if (i__ >= j) {
temp = (d__1 = a[i__ + j * a_dim1], abs(d__1));
} else {
temp = (d__1 = a[j + i__ * a_dim1], abs(d__1));
}
}
symb_zero__ = symb_zero__ && (x[j] == 0. || temp == 0.);
y[iy] += *alpha * (d__1 = x[j], abs(d__1)) * temp;
}
}
if (! symb_zero__) {
y[iy] += d_sign(&safe1, &y[iy]);
}
iy += *incy;
}
} else {
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
if (*beta == 0.) {
symb_zero__ = TRUE_;
y[iy] = 0.;
} else if (y[iy] == 0.) {
symb_zero__ = TRUE_;
} else {
symb_zero__ = FALSE_;
y[iy] = *beta * (d__1 = y[iy], abs(d__1));
}
jx = kx;
if (*alpha != 0.) {
i__2 = *n;
for (j = 1; j <= i__2; ++j) {
if (*uplo == ilauplo_("U")) {
if (i__ <= j) {
temp = (d__1 = a[i__ + j * a_dim1], abs(d__1));
} else {
temp = (d__1 = a[j + i__ * a_dim1], abs(d__1));
}
} else {
if (i__ >= j) {
temp = (d__1 = a[i__ + j * a_dim1], abs(d__1));
} else {
temp = (d__1 = a[j + i__ * a_dim1], abs(d__1));
}
}
symb_zero__ = symb_zero__ && (x[j] == 0. || temp == 0.);
y[iy] += *alpha * (d__1 = x[jx], abs(d__1)) * temp;
jx += *incx;
}
}
if (! symb_zero__) {
y[iy] += d_sign(&safe1, &y[iy]);
}
iy += *incy;
}
}
return 0;
/* End of DLA_SYAMV */
} /* dla_syamv__ */
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