## Developer Reference

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

# ?rotm

Performs modified Givens rotation of points in the plane.

## Syntax

Include Files
• mkl.fi
,
blas.f90
Description
Given two vectors
x
and
y
, each vector element of these vectors is replaced as follows: for
i
=1 to
n
, where
H
is a modified Givens transformation matrix whose values are stored in the
param
(2)
through
param
(5)
array. See discussion on the
param
argument.
Input Parameters
n
INTEGER
.
Specifies the number of elements in vectors
x
and
y
.
x
REAL
for
srotm
DOUBLE PRECISION
for
drotm
Array, size at least
(1 + (
n
-1)*abs(
incx
))
.
incx
INTEGER
.
Specifies the increment for the elements of
x
.
y
REAL
for
srotm
DOUBLE PRECISION
for
drotm
Array, size at least
(1 + (
n
-1)*abs(
incy
))
.
incy
INTEGER
.
Specifies the increment for the elements of
y
.
param
REAL
for
srotm
DOUBLE PRECISION
for
drotm
Array, size 5.
The elements of the
param
array are:
param
(1)
contains a switch,
flag
.
param
(2-5)
contain
h
11
,
h
21
,
h
12
, and
h
22
, respectively, the components of the array
H
.
Depending on the values of
flag
, the components of
H
are set as follows:
flag
=
-1.0
: flag
=
0.0
: flag
=
1.0
: flag
=
-2.0
: In the last three cases, the matrix entries of 1.0, -1.0, and 0.0 are assumed based on the value of
flag
and are not required to be set in the
param
vector.
Output Parameters
x
Each element
x(i)
is replaced by
h
11
*
x(i)
+
h
12
*
y(i)
.
y
Each element
y(i)
is replaced by
h
21
*
x(i)
+
h
22
*
y(i)
.
BLAS 95 Interface Notes
Routines in Fortran 95 interface have fewer arguments in the calling sequence than their FORTRAN 77 counterparts. For general conventions applied to skip redundant or reconstructible arguments, see BLAS 95 Interface Conventions.
Specific details for the routine
rotm
interface are the following:
x
Holds the vector with the number of elements
n
.
y
Holds the vector with the number of elements
n
.