# ?geru

Performs a rank-1 update (unconjugated) of a general matrix.

## Syntax

FORTRAN 77:

call cgeru(m, n, alpha, x, incx, y, incy, a, lda )

call zgeru(m, n, alpha, x, incx, y, incy, a, lda )

Fortran 95:

call geru(a, x, y [,alpha])

## Description

The ?geru routines perform a matrix-vector operation defined as
`A := alpha*x*y ' + A,`

where:

alpha is a scalar,

x is an m-element vector,

y is an n-element vector,

A is an m-by-n matrix.

## Input Parameters

m

  INTEGER. Specifies the number of rows of the matrix A.

  The value of m must be at least zero.

n

  INTEGER. Specifies the number of columns of the matrix A.

  The value of n must be at least zero.

alpha

  COMPLEX for cgeru

  DOUBLE COMPLEX for zgeru

  Specifies the scalar alpha.

x

  COMPLEX for cgeru

  DOUBLE COMPLEX for zgeru

  Array, DIMENSION at least `(1 + (m - 1)*abs(incx))`. Before entry, the incremented array x must contain the m-element vector x.

incx

  INTEGER. Specifies the increment for the elements of x.

  The value of incx must not be zero.

y

  COMPLEX for cgeru

  DOUBLE COMPLEX for zgeru

  Array, DIMENSION at least `(1 + (n - 1)*abs(incy))`. Before entry, the incremented array y must contain the n-element vector y.

incy

  INTEGER. Specifies the increment for the elements of y.

  The value of incy must not be zero.

a

  COMPLEX for cgeru

  DOUBLE COMPLEX for zgeru

  Array, DIMENSION `(lda, n)`.

  Before entry, the leading m-by-n part of the array a must contain the matrix of coefficients.

lda

  INTEGER. Specifies the first dimension of a as declared in the calling (sub)program. The value of lda must be at least `max(1, m)`.

## Output Parameters

a

  Overwritten by the updated matrix.

## Fortran 95 Interface Notes

Routines in Fortran 95 interface have fewer arguments in the calling sequence than their FORTRAN 77 counterparts. For general conventions applied to skip redundant or reconstructible arguments, see Fortran 95 Interface Conventions.

Specific details for the routine geru interface are the following:

a

  Holds the matrix A of size (m,n).

x

  Holds the vector of length (m).

y

  Holds the vector of length (n).

alpha

  The default value is 1.

Parent topic: BLAS Level 2 Routines