Contents

# p?lauu2

Computes the product
U
*
U
'
or
L
'*
L
, where
U
and
L
are upper or lower triangular matrices (local unblocked algorithm).

## Syntax

Include Files
• mkl_scalapack.h
Description
The
p?lauu2
function
computes the product
U*U
' or
L'*L
, where the triangular factor
U
or
L
is stored in the upper or lower triangular part of the distributed matrix
sub(
A
)=
A
(
ia
:
ia
+
n
-1,
ja
:
ja
+
n
-1)
.
If
uplo
=
'U'
or
'u'
, then the upper triangle of the result is stored, overwriting the factor
U
in sub(
A
).
If
uplo
=
'L'
or
'l'
, then the lower triangle of the result is stored, overwriting the factor
L
in sub(
A
).
This is the unblocked form of the algorithm, calling BLAS Level 2 Routines. No communication is performed by this
function
, the matrix to operate on should be strictly local to one process.
Input Parameters
uplo
(global)
Specifies whether the triangular factor stored in the
matrix
sub(
A
) is upper or lower triangular:
=
U
: upper triangular
=
L
: lower triangular.
n
(global)
The number of rows and columns to be operated on, that is, the order of the triangular factor
U
or
L
.
n
0
.
a
(local)
Pointer into the local memory to an array of size
lld_a
*
LOCc
(
ja
+
n
-1)
. On entry, the local pieces of the triangular factor
U
or
L
.
ia
(global)
The row index in the global matrix
A
indicating the first row of sub(
A
).
ja
(global)
The column index in the global matrix
A
indicating the first column of sub(
A
).
desca
(global and local) array of size
dlen_
. The array descriptor for the distributed matrix
A
.
Output Parameters
a
(local)
On exit, if
uplo
=
'U'
, the upper triangle of the distributed matrix sub(
A
) is overwritten with the upper triangle of the product
U*U
'; if
uplo
=
'L'
, the lower triangle of sub(
A
) is overwritten with the lower triangle of the product
L
'*
L
.

#### Product and Performance Information

1

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