Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

?rotg

Computes the parameters for a Givens rotation.

Syntax

call srotg
(
a
,
b
,
c
,
s
)
call drotg
(
a
,
b
,
c
,
s
)
call crotg
(
a
,
b
,
c
,
s
)
call zrotg
(
a
,
b
,
c
,
s
)
call rotg
(
a
,
b
,
c
,
s
)
Include Files
  • mkl.fi
    ,
    blas.f90
Description
Given the Cartesian coordinates
(
a
,
b
)
of a point,
these
routines return the parameters
c
,
s
,
r
, and
z
associated with the Givens rotation. The parameters
c
and
s
define a unitary matrix such that:
Equation
The parameter
z
is defined such that if |
a
| > |
b
|,
z
is
s
; otherwise if
c
is not 0
z
is 1/
c
; otherwise
z
is 1.
See a more accurate LAPACK version
?lartg
.
Input Parameters
a
REAL
for
srotg
DOUBLE PRECISION
for
drotg
COMPLEX
for
crotg
DOUBLE COMPLEX
for
zrotg
Provides the
x
-coordinate of the point
p
.
b
REAL
for
srotg
DOUBLE PRECISION
for
drotg
COMPLEX
for
crotg
DOUBLE COMPLEX
for
zrotg
Provides the
y
-coordinate of the point
p
.
Output Parameters
a
Contains
the parameter
r
associated with the Givens rotation.
b
Contains
the parameter
z
associated with the Givens rotation.
c
REAL
for
srotg
DOUBLE PRECISION
for
drotg
REAL
for
crotg
DOUBLE PRECISION
for
zrotg
Contains
the parameter
c
associated with the Givens rotation.
s
REAL
for
srotg
DOUBLE PRECISION
for
drotg
COMPLEX
for
crotg
DOUBLE COMPLEX
for
zrotg
Contains
the parameter
s
associated with the Givens rotation.