Contents

# p?getf2

Computes an LU factorization of a general matrix, using partial pivoting with row interchanges (local blocked algorithm).

## Syntax

Include Files
• mkl_scalapack.h
Description
The
p?getf2
function
computes an
LU
factorization of a general
m
-by-
n
distributed matrix sub(
A
) =
A
(
ia
:
ia
+
m
-1
,
ja
:
ja
+
n
-1)
using partial pivoting with row interchanges.
The factorization has the form
sub(
A
) =
P
*
L
*
U
, where
P
is a permutation matrix,
L
is lower triangular with unit diagonal elements (lower trapezoidal if
m
>
n
), and
U
is upper triangular (upper trapezoidal if
m
<
n
). This is the right-looking Parallel Level 2 BLAS version of the algorithm.
Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.
Notice revision #20201201
Input Parameters
m
(global)
The number of rows in the distributed matrix sub(
A
).
(
m
≥0)
.
n
(global) The number of columns in the distributed matrix sub(
A
).
(
nb_a
-
mod
(
ja
-1,
nb_a
)
n
0)
.
a
(local).
Pointer into the local memory to an array of size
lld_a
*
LOC
c
(
ja
+
n
-1)
.
On entry, this array contains the local pieces of the
m
-by-
n
distributed matrix sub(
A
).
ia
,
ja
(global) The row and column indices in the global matrix
A
indicating the first row and the first column of the matrix sub(
A
), respectively.
desca
(global and local) array of size
dlen_
. The array descriptor for the distributed matrix
A
.
Output Parameters
ipiv
(local)
Array of size
(
LOCr
(
m_a
) +
mb_a
)
. This array contains the pivoting information.
ipiv
[
i
]
-
>
The global row that local row
(
i
+1)
was swapped with
,
i
= 0, 1, ... ,
LOCr
(
m_a
) +
mb_a
- 1
. This array is tied to the distributed matrix
A
.
info
(local).
If
info
= 0
: successful exit.
If
info
< 0:
• if the
i
-th argument is an array and the
j
-th entry
, indexed
j
-1,
info
= -(
i
*100+
j
)
,
• if the
i
-th argument is a scalar and had an illegal value, then
info
=
- i
.
If
info
>
0
: If
info
=
k
, the matrix element
U
(
ia
+
k
-1
,
ja
+
k
-1)
is exactly zero. The factorization has been completed, but the factor
U
is exactly singular, and division by zero will occur if it is used to solve a system of equations.

#### Product and Performance Information

1

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