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

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804