NAG Library Routine Document

f06hmf (zrot)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06hmf (zrot) applies a plane rotation with a real cosine and complex sine to two complex vectors.

2
Specification

Fortran Interface
Subroutine f06hmf ( n, cx, incx, cy, incy, c, s)
Integer, Intent (In):: n, incx, incy
Real (Kind=nag_wp), Intent (In):: c
Complex (Kind=nag_wp), Intent (In):: s
Complex (Kind=nag_wp), Intent (Inout):: cx(*), cy(*)
C Header Interface
#include nagmk26.h
void  f06hmf_ (const Integer *n, Complex cx[], const Integer *incx, Complex cy[], const Integer *incy, const double *c, const Complex *s)
The routine may be called by its LAPACK name zrot.

3
Description

f06hmf (zrot) applies a plane rotation, where the cosine is real and the sine is complex, to two n-element complex vectors x and y:
xT yT c s -s- c xT yT .  

4
References

None.

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x and y.
2:     cx* – Complex (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array cx must be at least max1, 1+n-1 ×incx .
On entry: the n-element vector x.
If incx>0, xi must be stored in cx1+i-1×incx, for i=1,2,,n.
If incx<0, xi must be stored in cx1-n-i×incx, for i=1,2,,n.
Intermediate elements of cx are not referenced.
On exit: the transformed vector x stored in the array elements used to supply the original vector x.
Intermediate elements of cx are unchanged.
3:     incx – IntegerInput
On entry: the increment in the subscripts of cx between successive elements of x.
4:     cy* – Complex (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array cy must be at least max1, 1+n-1 ×incy .
On entry: the n-element vector y.
If incy>0, yi must be stored in cy1+i-1×incy, for i=1,2,,n.
If incy<0, yi must be stored in cy1-n-i×incy, for i=1,2,,n.
Intermediate elements of cy are not referenced.
On exit: the transformed vector y.
Intermediate elements of cy are unchanged.
5:     incy – IntegerInput
On entry: the increment in the subscripts of cy between successive elements of y.
6:     c – Real (Kind=nag_wp)Input
On entry: the value c, the cosine of the rotation.
7:     s – Complex (Kind=nag_wp)Input
On entry: the value s, the sine of the rotation.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06hmf (zrot) is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017