?rotmg

Syntax

FORTRAN 77:

call srotmg(d1, d2, x1, y1, param)

call drotmg(d1, d2, x1, y1, param)

Fortran 95:

call rotmg(d1, d2, x1, y1, param)

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

Given Cartesian coordinates (x1, y1) of an input vector, these routines compute the components of a modified Givens transformation matrix H that zeros the y-component of the resulting vector:

Input Parameters

d1

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the scaling factor for the x-coordinate of the input vector.

d2

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the scaling factor for the y-coordinate of the input vector.

x1

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the x-coordinate of the input vector.

y1

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the y-coordinate of the input vector.

Output Parameters

d1

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the first diagonal element of the updated matrix.

d2

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the second diagonal element of the updated matrix.

x1

REAL for srotmg

DOUBLE PRECISION for drotmg

Provides the x-coordinate of the rotated vector before scaling.

param

REAL for srotmg

DOUBLE PRECISION for drotmg

Array, DIMENSION 5.

The elements of the param array are:

param(1) contains a switch, flag. param(2-5) contain h11, h21, h12, and h22, respectively, the components of the array H.

Depending on the values of flag, the components of H are set as follows:

In the last three cases, the matrix entries of 1., -1., and 0. are assumed based on the value of flag and are not required to be set in the param vector.