?spmv

Syntax

FORTRAN 77:

call sspmv(uplo, n, alpha, ap, x, incx, beta, y, incy)

call dspmv(uplo, n, alpha, ap, x, incx, beta, y, incy)

Fortran 95:

call spmv(ap, x, y [,uplo][,alpha] [,beta])

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 ?spmv routines perform a matrix-vector operation defined as y := alpha*A*x + beta*y,

where:

alpha and beta are scalars,

x and y are n-element vectors,

A is an n-by-n symmetric matrix, supplied in packed form.

Input Parameters

uplo

CHARACTER*1. Specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array ap.

If uplo = 'U' or 'u', then the upper triangular part of the matrix A is supplied in the packed array ap .

If uplo = 'L' or 'l', then the low triangular part of the matrix A is supplied in the packed array ap .

n

INTEGER. Specifies the order of the matrix A. The value of n must be at least zero.

alpha

REAL for sspmv

DOUBLE PRECISION for dspmv

Specifies the scalar alpha.

ap

REAL for sspmv

DOUBLE PRECISION for dspmv

Array, DIMENSION at least ((n*(n + 1))/2).

Before entry with uplo = 'U' or 'u', the array ap must contain the upper triangular part of the symmetric matrix packed sequentially, column-by-column, so that ap(1) contains a(1,1), ap(2) and ap(3) contain a(1,2) and a(2, 2) respectively, and so on. Before entry with uplo = 'L' or 'l', the array ap must contain the lower triangular part of the symmetric matrix packed sequentially, column-by-column, so that ap(1) contains a(1,1), ap(2) and ap(3) contain a(2,1) and a(3,1) respectively, and so on.

x

REAL for sspmv

DOUBLE PRECISION for dspmv

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

incx

INTEGER. Specifies the increment for the elements of x.

The value of incx must not be zero.

beta

REAL for sspmv

DOUBLE PRECISION for dspmv

Specifies the scalar beta.

When beta is supplied as zero, then y need not be set on input.

y

REAL for sspmv

DOUBLE PRECISION for dspmv

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.

Output Parameters

y

Overwritten by the 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 spmv interface are the following:

ap

Holds the array ap of size (n*(n+1)/2).

x

Holds the vector with the number of elements n.

y

Holds the vector with the number of elements n.

uplo

Must be 'U' or 'L'. The default value is 'U'.

alpha

The default value is 1.

beta

The default value is 0.