---
name: "zsymv"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/zsymv/3lapack"
---

# zsymv(3lapack)

performs the matrix-vector operation y := alpha\*A\*x + beta\*y,

## NAME

ZSYMV - performs the matrix-vector operation   y := alpha\*A\*x + beta\*y,

## SYNOPSIS

- SUBROUTINE ZSYMV(

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

- CHARACTER

  UPLO

- INTEGER

  INCX, INCY, LDA, N

- COMPLEX\*16

  ALPHA, BETA

- COMPLEX\*16

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

## PURPOSE

ZSYMV  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\*16

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

- A (input) COMPLEX\*16 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\*16 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\*16

  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\*16 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.