Contents

# cblas_?symm

Computes a matrix-matrix product where one input matrix is symmetric.

## Syntax

Include Files
• mkl.h
Description
The
?symm
routines compute a scalar-matrix-matrix product
with one symmetric matrix and add the result to a scalar-matrix product
.
The operation is defined as
`C := alpha*A*B + beta*C,`
or
`C := alpha*B*A + beta*C,`
where:
alpha
and
beta
are scalars,
A
is a symmetric matrix,
B
and
C
are
m
-by-
n
matrices.
Input Parameters
Layout
Specifies whether two-dimensional array storage is row-major (
CblasRowMajor
) or column-major (
CblasColMajor
).
side
Specifies whether the symmetric matrix
A
appears on the left or right in the operation:
if
side
=
CblasLeft
, then
C
:=
alpha
*
A
*
B
+
beta
*
C
;
if
side
=
CblasRight
, then
C
:=
alpha
*
B
*
A
+
beta
*
C
.
uplo
Specifies whether the upper or lower triangular part of the symmetric matrix
A
is used:
if
uplo
=
CblasUpper
, then the upper triangular part is used;
if
uplo
=
CblasLower
, then the lower triangular part is used.
m
Specifies the number of rows of the matrix
C
.
The value of
m
must be at least zero.
n
Specifies the number of columns of the matrix
C
.
The value of
n
must be at least zero.
alpha
Specifies the scalar
alpha
.
a
Array, size
lda
*
ka
, where
ka
is
m
when
side
=
CblasLeft
and is
n
otherwise.
Before entry with
side
=
CblasLeft
, the
m
-by-
m
part of the array
a
must contain the symmetric matrix, such that when
uplo
=
CblasUpper
m
-by-
m
upper triangular part of the array
a
must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of
a
is not referenced, and when
side
=
CblasLeft
m
-by-
m
lower triangular part of the array
a
must contain the lower triangular part of the symmetric matrix and the strictly upper triangular part of
a
is not referenced.
Before entry with
side
=
CblasRight
, the
n
-by-
n
part of the array
a
must contain the symmetric matrix, such that when
uplo
=
CblasUpper
e array
a
must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of
a
is not referenced, and when
side
=
CblasLeft
n
-by-
n
lower triangular part of the array
a
must contain the lower triangular part of the symmetric matrix and the strictly upper triangular part of
a
is not referenced.
lda
a
as declared in the calling (sub)program. When
side
=
CblasLeft
then
lda
must be at least
max(1,
m
)
, otherwise
lda
must be at least
max(1,
n
)
.
b
For
Layout
=
CblasColMajor
: array, size
ldb
*
n
.
m
-by-
n
part of the array
b
must contain the matrix
B
.
For
Layout
=
CblasRowMajor
: array, size
ldb
*
m
n
-by-
m
part of the array
b
must contain the matrix
B
ldb
b
as declared in the calling (sub)program.
When
Layout
=
CblasColMajor
,
ldb
must be at least
max(1,
m
)
; otherwise,
ldb
must be at least
max(1,
n
)
.
beta
Specifies the scalar
beta
.
When
beta
is set to zero, then
c
need not be set on input.
c
For
Layout
=
CblasColMajor
: array, size
ldc
*
n
m
-by-
n
part of the array
c
must contain the matrix
C
, except when
beta
is zero, in which case
c
need not be set on entry.
For
Layout
=
CblasRowMajor
: array, size
ldc
*
m
n
-by-
m
part of the array
c
must contain the matrix
C
, except when
beta
is zero, in which case
c
need not be set on entry.
ldc
c
as declared in the calling (sub)program.
When
Layout
=
CblasColMajor
,
ldc
must be at least
max(1,
m
)
; otherwise,
ldc
must be at least
max(1,
n
)
.
Output Parameters
c
Overwritten by the
m
-by-
n
updated matrix.

#### Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.