?dot

Syntax

FORTRAN 77:

res = sdot(n, x, incx, y, incy)

res = ddot(n, x, incx, y, incy)

Fortran 95:

res = dot(x, y)

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 ?dot routines perform a vector-vector reduction operation defined as

where x_i and y_i are elements of vectors x and y.

Input Parameters

n

INTEGER. Specifies the number of elements in vectors x and y.

x

REAL for sdot

DOUBLE PRECISION for ddot

Array, DIMENSION at least (1+(n-1)*abs(incx)).

incx

INTEGER. Specifies the increment for the elements of x.

y

REAL for sdot

DOUBLE PRECISION for ddot

Array, DIMENSION at least (1+(n-1)*abs(incy)).

incy

INTEGER. Specifies the increment for the elements of y.

Output Parameters

res

REAL for sdot

DOUBLE PRECISION for ddot

Contains the result of the dot product of x and y, if n is positive. Otherwise, res contains 0.

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 dot interface are the following:

x

Holds the vector with the number of elements n.

y

Holds the vector with the number of elements n.