?gemv

Syntax

FORTRAN 77:

call sgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

call dgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

call cgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

call zgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

call scgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

call dzgemv(trans, m, n, alpha, a, lda, x, incx, beta, y, incy)

Fortran 95:

call gemv(a, x, y [,alpha][,beta] [,trans])

Include Files

The FORTRAN 77 interfaces are specified in the mkl_blas.fi include file, the Fortran 95 interfaces are specified in the blas.f90 include file, and the C interfaces are specified in the mkl_blas.h include file.

Description

The ?gemv routines perform a matrix-vector operation defined as

y := alpha*A*x + beta*y,

or

y := alpha*A'*x + beta*y,

or

y := alpha*conjg(A')*x + beta*y,

where:

alpha and beta are scalars,

x and y are vectors,

A is an m-by-n matrix.

Input Parameters

trans

CHARACTER*1. Specifies the operation:

if trans= 'N' or 'n', then y := alpha*A*x + beta*y;

if trans= 'T' or 't', then y := alpha*A'*x + beta*y;

if trans= 'C' or 'c', then y := alpha *conjg(A')*x + beta*y.

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

REAL for sgemv

DOUBLE PRECISION for dgemv

COMPLEX for cgemv, scgemv

DOUBLE COMPLEX for zgemv, dzgemv

Specifies the scalar alpha.

a

REAL for sgemv, scgemv

DOUBLE PRECISION for dgemv, dzgemv

COMPLEX for cgemv

DOUBLE COMPLEX for zgemv

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

x

REAL for sgemv

DOUBLE PRECISION for dgemv

COMPLEX for cgemv, scgemv

DOUBLE COMPLEX for zgemv, dzgemv

Array, DIMENSION at least (1+(n-1)*abs(incx)) when trans = 'N' or 'n' and at least (1+(m - 1)*abs(incx)) otherwise. Before entry, the incremented array x must contain the vector x.

incx

INTEGER. Specifies the increment for the elements of x.

The value of incx must not be zero.

beta

REAL for sgemv

DOUBLE PRECISION for dgemv

COMPLEX for cgemv, scgemv

DOUBLE COMPLEX for zgemv, dzgemv

Specifies the scalar beta. When beta is set to zero, then y need not be set on input.

y

REAL for sgemv

DOUBLE PRECISION for dgemv

COMPLEX for cgemv, scgemv

DOUBLE COMPLEX for zgemv, dzgemv

Array, DIMENSION at least (1 +(m - 1)*abs(incy)) when trans = 'N' or 'n' and at least (1 +(n - 1)*abs(incy)) otherwise. Before entry with non-zero beta, the incremented array y must contain the vector y.

incy

INTEGER. Specifies the increment for the elements of y.

The value of incy must not be zero.

Output Parameters

y

Updated vector y.

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 gemv interface are the following:

a

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

x

Holds the vector with the number of elements rx where rx = n if trans = 'N', rx = m otherwise.

y

Holds the vector with the number of elements ry where ry = m if trans = 'N', ry = n otherwise.

trans

Must be 'N', 'C', or 'T'.

The default value is 'N'.

alpha

The default value is 1.

beta

The default value is 0.