Contents

# p?atrmv

Computes a distributed matrix-vector product using absolute values for a triangular matrix.

## Syntax

Include Files
• mkl_pblas.h
Description
The
p?atrmv
routines perform one of the following distributed matrix-vector operations defined as
sub(
y
) := abs(
alpha
)*abs(sub(
A
))*abs(sub(
x
))+ abs(
beta
*sub(
y
))
, or
sub(
y
) := abs(
alpha
)*abs(sub(
A
)')*abs(sub(
x
))+ abs(
beta
*sub(
y
))
, or
sub(
y
) := abs(
alpha
)*abs(conjg(sub(
A
)'))*abs(sub(
x
))+ abs(
beta
*sub(
y
))
,
where:
alpha
and
beta
are scalars,
sub(
A
)
is a
n
-by-
n
unit, or non-unit, upper or lower triangular distributed matrix,
sub(
A
) =
A
(
ia
:
ia
+
n
-1,
ja
:
ja
+
n
-1)
,
sub(
x
)
is an
n
-element distributed vector.
sub(
x
)
denotes
X
(
ix
,
jx
:
jx
+
n
-1)
if
incx
=
m_x
, and
X
(
ix
:
ix
+
n
-1,
jx
)
if
incx
= 1
.
Input Parameters
uplo
(global) Specifies whether the distributed matrix
sub(
A
)
is upper or lower triangular:
if
uplo
=
'U'
or
'u'
, then the matrix is upper triangular;
if
uplo
=
'L'
or
'l'
, then the matrix is low triangular.
trans
(global) Specifies the form of
op(sub(
A
))
used in the matrix equation:
if
trans
= '
N
'
or
'
n
'
, then
sub(
y
) := |
alpha
|*|sub(
A
)|*|sub(
x
)
|+|
beta
*sub(
y
)|;
if
trans
= '
T
'
or
'
t
'
, then
sub(
y
) := |
alpha
|*|sub(
A
)'|*|sub(
x
)
|+|
beta
*sub(
y
)|;
if
trans
= '
C
'
or
'
c
'
, then
sub(
y
) := |
alpha
|*|conjg(sub(
A
)')|*|sub(
x
)|+|
beta
*sub(
y
)|
.
diag
(global) Specifies whether the matrix
sub(
A
)
is unit triangular:
if
diag
=
'U'
or
'u'
then the matrix is unit triangular;
if
diag
=
'N'
or
'n'
, then the matrix is not unit triangular.
n
(global) Specifies the order of the distributed matrix
sub(
A
)
,
n
0.
alpha
(global)
Specifies the scalar
alpha
.
a
(local)
Array, size at least
(
lld_a
, LOCq(1,
ja
+
n
-1))
.
Before entry with
uplo
=
'U'
or
'u'
, this array contains the local entries corresponding to the entries of the upper triangular distributed matrix
sub(
A
)
, and the local entries corresponding to the entries of the strictly lower triangular part of the distributed matrix
sub(
A
)
is not referenced.
Before entry with
uplo
=
'L'
or
'l'
, this array contains the local entries corresponding to the entries of the lower triangular distributed matrix
sub(
A
)
, and the local entries corresponding to the entries of the strictly upper triangular part of the distributed matrix
sub(
A
)
is not referenced.
When
diag
=
'U'
or
'u'
, the local entries corresponding to the diagonal elements of the submatrix
sub(
A
)
are not referenced either, but are assumed to be unity.
ia
,
ja
(global) The row and column indices in the distributed matrix
A
indicating the first row and the first column of the submatrix
sub(
A
)
, respectively.
desca
(global and local) array of dimension 9. The array descriptor of the distributed matrix
A
.
x
(local)
Array, size at least
(
jx
-1)*
m_x
+
ix
+(
n
-1)*abs(
incx
))
.
This array contains the entries of the distributed vector
sub(
x
)
.
ix
,
jx
(global) The row and column indices in the distributed matrix
X
indicating the first row and the first column of the submatrix
sub(
x
)
, respectively.
descx
(global and local) array of dimension 9. The array descriptor of the distributed matrix
X
.
incx
(global) Specifies the increment for the elements of
sub(
x
)
. Only two values are supported, namely 1 and
m_x
.
incx
must not be zero.
beta
(global)
Specifies the scalar
beta
. When
beta
is set to zero, then
sub(
y
)
need not be set on input.
y
(local)
Array, size
(
jy
-1)*
m_y
+
iy
+(
m
-1)*abs(
incy
))
when
trans
= '
N
'
or
'n'
, and
(
jy
-1)*
m_y
+
iy
+(
n
-1)*abs(
incy
))
otherwise.
This array contains the entries of the distributed vector
sub(
y
)
.
iy
,
jy
(global) The row and column indices in the distributed matrix
Y
indicating the first row and the first column of the submatrix
sub(
y
)
, respectively.
descy
(global and local) array of dimension 9. The array descriptor of the distributed matrix
Y
.
incy
(global) Specifies the increment for the elements of
sub(
y
)
. Only two values are supported, namely 1 and
m_y
.
incy
must not be zero.
Output Parameters
y
Overwritten by the transformed distributed vector
sub(
y
)
.

#### Product and Performance Information

1

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