NAG FL Interface
f06fpf (drots)

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1 Purpose

f06fpf applies a real symmetric plane rotation to two real vectors.

2 Specification

Fortran Interface
Subroutine f06fpf ( 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 <nag.h>
void  f06fpf_ (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 the names f06fpf or nagf_blas_drots.

3 Description

f06fpf applies a symmetric real plane rotation to two n-element real vectors x and y scattered with stride incx and incy respectively:
( xT yT ) ( c s s -c ) ( xT yT ) .  

4 References

None.

5 Arguments

1: n Integer Input
On entry: n, the number of elements in x and y.
2: x(*) Real (Kind=nag_wp) array Input/Output
Note: the dimension of the array x must be at least max(1, 1+(n-1) ×|incx| ) .
On entry: the original vector x.
If incx>0, xi must be stored in x(1+(i-1)×incx) , for i=1,2,,n.
If incx<0, xi must be stored in x(1-(n-i)×incx) , for i=1,2,,n.
Intermediate elements of x are not referenced.
On exit: the transformed vector x stored in the same elements used to supply the original vector x.
Intermediate elements of x are unchanged.
3: incx Integer Input
On entry: the increment in the subscripts of x between successive elements of x.
4: y(*) Real (Kind=nag_wp) array Input/Output
Note: the dimension of the array y must be at least max(1, 1+(n-1) ×|incy| ) .
On entry: the original vector y.
If incy>0, yi must be stored in y(1+(i-1)×incy) , for i=1,2,,n.
If incy<0, yi must be stored in y(1-(n-i)×incy) , for i=1,2,,n.
Intermediate elements of y are not referenced.
On exit: the transformed vector y stored in the same elements used to supply the original vector y.
Intermediate elements of y are unchanged.
5: incy Integer Input
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

Background information to multithreading can be found in the Multithreading documentation.
f06fpf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.