## Developer Reference

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

# ?symv

Computes a matrix-vector product for a symmetric matrix.

## Syntax

Include Files
• mkl.fi
,
blas.f90
Description
The
?symv
routines perform a matrix-vector operation defined as
`y := alpha*A*x + beta*y,`
where:
alpha
and
beta
are scalars,
x
and
y
are
n
-element vectors,
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
ssymv
DOUBLE PRECISION
for
dsymv
Specifies the scalar
alpha
.
a
REAL
for
ssymv
DOUBLE PRECISION
for
dsymv
Array, size
(
lda
,
n
)
.
Before entry with
uplo
=
'U'
or
'u'
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'
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
.
a
as declared in the calling (sub)program. The value of
lda
must be at least
max(1,
n
)
.
x
REAL
for
ssymv
DOUBLE PRECISION
for
dsymv
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.
beta
REAL
for
ssymv
DOUBLE PRECISION
for
dsymv
Specifies the scalar
beta
.
When
beta
is supplied as zero, then
y
need not be set on input.
y
REAL
for
ssymv
DOUBLE PRECISION
for
dsymv
Array, size at least
(1 + (
n
- 1)*abs(
incy
))
. Before entry, the incremented array
y
must contain the