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

# csyr(3lapack)

performs the symmetric rank 1 operation A := alpha\*x\*( x' ) + A,

## NAME

CSYR - performs the symmetric rank 1 operation   A := alpha\*x\*( x' ) + A,

## SYNOPSIS

- SUBROUTINE CSYR(

  UPLO, N, ALPHA, X, INCX, A, LDA )

- CHARACTER

  UPLO

- INTEGER

  INCX, LDA, N

- COMPLEX

  ALPHA

- COMPLEX

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

## PURPOSE

CSYR   performs the symmetric rank 1 operation where alpha is a complex scalar, x is an n element vector 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.

- 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.

- A (input/output) 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. On exit, the upper triangular part of the array A is overwritten by the upper triangular part of the updated matrix. 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. On exit, the lower triangular part of the array A is overwritten by the lower triangular part of the updated matrix.

- 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.