NAME
ssymv - perform the matrix-vector operation y := alpha*A*x
+ beta*y
SYNOPSIS
SUBROUTINE SSYMV ( UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y,
INCY )
REAL ALPHA, BETA
INTEGER INCX, INCY, LDA, N
CHARACTER*1 UPLO
REAL A( LDA, * ), X( * ), Y( * )
#include <sunperf.h>
void ssymv(char uplo, int n, float alpha, float *sa, int
lda, float *sx, int incx, float sbeta, float *sy,
int incy) ;
PURPOSE
SSYMV 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.
PARAMETERS
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 - REAL .
On entry, ALPHA specifies the scalar alpha.
Unchanged on exit.
A - REAL 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. 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.
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 - 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.
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