f06bhf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual

NAG Library Routine Document

f06bhf  (drot2)

▸▿ Contents

    1  Purpose
    2  Specification
    3  Description
    4  References
    5  Arguments
    6  Error Indicators and Warnings
    7  Accuracy
    8  Parallelism and Performance
    9  Further Comments
    10  Example

1
Purpose

f06bhf applies a real similarity rotation to a 2 by 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 nagmk26.h
void  f06bhf_ ( double *x, double *y, double *z, const double *c, const double *s)

3
Description

f06bhf applies a real similarity rotation, with parameters c and s, to a given 2 by 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.
f06bhf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017