NAG Library Manual, Mark 27.3
Interfaces:  FL   CL   CPP   AD 
NAG FL Interface Introduction
F06 (Blas) Chapter Contents
F06 (Blas) Chapter Introduction
f06bh:  FL   CL   CPP   AD 

NAG FL Interface
f06bhf (drot2)

NAG Library Manual, Mark 27.3
Interfaces:  FL   CL   CPP   AD 
NAG FL Interface Introduction
F06 (Blas) Chapter Contents
F06 (Blas) Chapter Introduction
f06bh:  FL   CL   CPP   AD 

▸▿ Contents

© The Numerical Algorithms Group Ltd. 2021
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1 Purpose

f06bhf applies a real similarity rotation to a 2×2 real symmetric matrix.

2 Specification

Fortran Interface
Subroutine f06bhf ( x, y, z, c, s)
Real (Kind=nag_wp), Intent (In) :: c, s
Real (Kind=nag_wp), Intent (Inout) :: x, y, z
C Header Interface
#include <nag.h>
void  f06bhf_ (double *x, double *y, double *z, const double *c, const double *s)
The routine may be called by the names f06bhf or nagf_blas_drot2.

3 Description

f06bhf applies a real similarity rotation, with parameters c and s, to a given 2×2 real symmetric matrix; that is, it performs the operation:
( x y y z ) ← ( c s -s c ) ( x y y z ) ( c -s s c ) .  

4 References

None.

5 Arguments

1: x – Real (Kind=nag_wp) Input/Output
On entry: the value x, the (1,1) element of the input matrix.
On exit: the transformed value x.
2: y – Real (Kind=nag_wp) Input/Output
On entry: the value y, the (1,2) or (2,1) element of the input matrix.
On exit: the transformed value y.
3: z – Real (Kind=nag_wp) Input/Output
On entry: the value z, the (2,2) element of the input matrix.
On exit: the transformed value z.
4: c – Real (Kind=nag_wp) Input
On entry: the value c, the cosine of the rotation.
5: 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

f06bhf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.
NAG Library Manual, Mark 27.3
Interfaces:  FL   CL   CPP   AD 
NAG FL Interface Introduction
F06 (Blas) Chapter Contents
F06 (Blas) Chapter Introduction
f06bh:  FL   CL   CPP   AD 
© The Numerical Algorithms Group Ltd. 2021