Developer Reference

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

?syr

Performs
a rank-1 update of a symmetric matrix.

Syntax

call ssyr
(
uplo
,
n
,
alpha
,
x
,
incx
,
a
,
lda
)
call dsyr
(
uplo
,
n
,
alpha
,
x
,
incx
,
a
,
lda
)
call syr
(
a
,
x
[
,
uplo
]
[
,
alpha
]
)
Include Files
  • mkl.fi
    ,
    blas.f90
Description
The
?syr
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.
Input Parameters
uplo
CHARACTER*1
.
Specifies whether the upper or lower triangular part of the array
a
is used.
If
uplo
=
'U'
or
'u'
, then the upper triangular part of the array
a
is used.
If
uplo
=
'L'
or
'l'
, then the low triangular part of the array
a
is used.
n
INTEGER
.
Specifies the order of the matrix
A
. The value of
n
must be at least zero.
alpha
REAL
for
ssyr
DOUBLE PRECISION
for
dsyr
Specifies the scalar
alpha
.
x
REAL
for
ssyr
DOUBLE PRECISION
for
dsyr
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.
a
REAL
for
ssyr
DOUBLE PRECISION
for
dsyr
Array, size
(
lda
,
n
)
.
Before entry with
uplo
=
'U'
or
'u'
, the leading
n
-by-
n
upper triangular part of the array
a
must contain the upper triangular part of the symmetric matrix
A
and the strictly lower triangular part of
a
is not referenced.
Before entry with
uplo
=
'L'
or
'l'
, the leading
n
-by-
n
lower triangular part of the array
a
must contain the lower triangular part of the symmetric matrix
A
and the strictly upper triangular part of
a
is not referenced.
lda
INTEGER
.
Specifies the leading dimension of
a
as declared in the calling (sub)program. The value of
lda
must be at least
max(1,
n
)
.
Output Parameters
a
With
uplo
=
'U'
or
'u'
, the upper triangular part of the array
a
is overwritten by the upper triangular part of the updated matrix.
With
uplo
=
'L'
or
'l'
, the lower triangular part of the array
a
is 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
syr
interface are the following:
a
Holds the matrix
A
<