Developer Reference

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

?spr

Performs a rank-1 update of a symmetric packed matrix.

Syntax

call sspr
(
uplo
,
n
,
alpha
,
x
,
incx
,
ap
)
call dspr
(
uplo
,
n
,
alpha
,
x
,
incx
,
ap
)
call spr
(
ap
,
x
[
,
uplo
]
[
,
alpha
]
)
Include Files
  • mkl.fi
    ,
    blas.f90
Description
The
?spr
routines perform a matrix-vector operation defined as
a
:=
alpha
*
x
*
x
'+
A
,
where:
alpha
is a real scalar,
x
is an
n
-element vector,
A
is an
n
-by-
n
symmetric matrix, supplied in packed form.
Input Parameters
uplo
CHARACTER*1
.
Specifies whether the upper or lower triangular part of the matrix
A
is supplied in the packed array
ap
.
If
uplo
=
'U'
or
'u'
, then the upper triangular part of the matrix
A
is supplied in the packed array
ap
.
If
uplo
=
'L'
or
'l'
, then the low triangular part of the matrix
A
is supplied in the packed array
ap
.
n
INTEGER
.
Specifies the order of the matrix
A
. The value of
n
must be at least zero.
alpha
REAL
for
sspr
DOUBLE PRECISION
for
dspr
Specifies the scalar
alpha
.
x
REAL
for
sspr
DOUBLE PRECISION
for
dspr
Array, size at least
(1 + (
n
- 1)*abs(
incx
))
. Before entry, the incremented array
x
must contain the
n
-element vector
x
.
incx
INTEGER
.
Specifies the increment for the elements of
x
.
The value of
incx
must not be zero.
ap
REAL
for
sspr
DOUBLE PRECISION
for
dspr
Before entry with
uplo
=
'U'
or
'u'
, the array
ap
must contain the upper triangular part of the symmetric matrix packed sequentially, column-by-column, so that
ap
(1)
contains
A
1, 1
,
ap
(2)
and
ap
(3)
contain
A
1, 2
and
A
2, 2
respectively, and so on.
Before entry with
uplo
=
'L'
or
'l'
, the array
ap
must contain the lower triangular part of the symmetric matrix packed sequentially, column-by-column, so that
ap
(1)
contains
A
1, 1
,
ap
(2)
and
ap
(3)
contain
A
2, 1
and
A
3, 1
respectively, and so on.
Output Parameters
ap
With
uplo
=
'U'
or
'u'
, overwritten by the upper triangular part of the updated matrix.
With
uplo
=
'L'
or
'l'
, overwritten by the lower triangular part of the updated matrix.
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
spr
interface are the following:
ap
Holds the array
ap
of size (
n*(