[ Previous  Next  Table of Contents  Index  Library Home 
Legal 
Search ]
Technical Reference: Base Operating System and Extensions , Volume 2
Performs matrixvector operations
using a symmetric matrix.
BLAS Library
(libblas.a)
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(*)
SUBROUTINE DSYMV(UPLO, N, ALPHA, A, LDA,
X, INCX, BETA, Y, INCY)
DOUBLE PRECISION ALPHA,BETA
INTEGER INCX,INCY,LDA,N
CHARACTER*1 UPLO
DOUBLE PRECISION A(LDA,*), X(*), Y(*)
The SSYMV or
DSYMV subroutine performs the matrixvector 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.
UPLO
 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
 On entry, N specifies the order of the matrix
A; N must be at least 0; unchanged on
exit.

ALPHA
 On entry, ALPHA specifies the scalar alpha; unchanged on
exit.

A
 An array of dimension ( LDA, N ); on 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; the
strictly lower triangular part of A is not referenced; on
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; the
strictly upper triangular part of A is not referenced;
unchanged on exit.

LDA
 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
 A vector of dimension at least (1 + (N1) * abs(
INCX ) ); on entry, the incremented array X must
contain the N element vector x; unchanged on exit.

INCX
 On entry, INCX specifies the increment for the elements of
X; INCX must not be 0; unchanged on
exit.

BETA
 On entry, BETA specifies the scalar beta; when
BETA is supplied as 0 then Y need not be set on input;
unchanged on exit.

Y
 A vector of dimension at least (1 + (N1) * abs(
INCY ) ); on entry, the incremented array Y must
contain the N element vector y; on exit, Y is
overwritten by the updated vector y.

INCY
 On entry, INCY specifies the increment for the elements of
Y; INCY must not be 0; unchanged on
exit.

[ Previous  Next  Table of Contents  Index 
Library Home 
Legal 
Search ]