SYNOPSIS

SUBROUTINE CSYMV(

UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )

    

CHARACTER UPLO

    

INTEGER INCX, INCY, LDA, N

    

COMPLEX ALPHA, BETA

    

COMPLEX A( LDA, * ), X( * ), Y( * )

PURPOSE

CSYMV performs the matrix-vector operation where alpha and beta are scalars, x and y are n element vectors and A is an n by n symmetric matrix.

ARGUMENTS

UPLO (input) 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 (input) INTEGER

On entry, N specifies the order of the matrix A. N must be at least zero. Unchanged on exit.

ALPHA (input) COMPLEX

On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

A (input) COMPLEX array, 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 (input) 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 (input) COMPLEX array, 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 (input) INTEGER

On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit.

BETA (input) COMPLEX

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 (input/output) COMPLEX array, 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 (input) INTEGER

On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.