NAG Library Routine Document

f06epf  (drot)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06epf (drot) applies a real plane rotation to two real vectors.

2
Specification

Fortran Interface
Subroutine f06epf ( n, x, incx, y, incy, c, s)
Integer, Intent (In):: n, incx, incy
Real (Kind=nag_wp), Intent (In):: c, s
Real (Kind=nag_wp), Intent (Inout):: x(*), y(*)
C Header Interface
#include nagmk26.h
void  f06epf_ ( const Integer *n, double x[], const Integer *incx, double y[], const Integer *incy, const double *c, const double *s)
The routine may be called by its BLAS name drot.

3
Description

f06epf (drot) applies a real plane rotation to two n-element real vectors x and y:
xT yT c s -s c xT yT .  
with stride incx and incy respectively. The plane rotation has the form generated by f06aaf (drotg) or f06baf.

4
References

Lawson C L, Hanson R J, Kincaid D R and Krogh F T (1979) Basic linear algebra supbrograms for Fortran usage ACM Trans. Math. Software 5 308–325

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x and y.
2:     x* – Real (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array x must be at least max1, 1+n-1 ×incx .
On entry: the n-element vector x.
If incx>0, xi must be stored in x1+i-1×incx, for i=1,2,,n.
If incx<0, xi must be stored in x1-n-i×incx, for i=1,2,,n.
Intermediate elements of x are not referenced.
On exit: the transformed vector x stored in the array elements used to supply the original vector x.
Intermediate elements of x are unchanged.
3:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
4:     y* – Real (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array y must be at least max1, 1+n-1 ×incy .
On entry: the n-element vector y.
If incy>0, yi must be stored in y1+i-1×incy, for i=1,2,,n.
If incy<0, yi must be stored in y1-n-i×incy, for i=1,2,,n.
Intermediate elements of y are not referenced.
On exit: the transformed vector y stored in the array elements used to supply the original vector y.
Intermediate elements of y are unchanged.
5:     incy – IntegerInput
On entry: the increment in the subscripts of y between successive elements of y.
6:     c – Real (Kind=nag_wp)Input
On entry: the value c, the cosine of the rotation.
7:     s – Real (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

f06epf (drot) is not threaded in any implementation.

9
Further Comments

None.

10
Example

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