## Developer Reference

• 2020.2
• 07/15/2020
• Public Content
Contents

# p?trti2

Computes the inverse of a triangular matrix (local unblocked algorithm).

## Syntax

Description
The
p?trti2
routine
computes the inverse of a real/complex upper or lower triangular block matrix sub
(
A
) =
A
(
ia
:
ia
+
n
-1
,
ja
:
ja
+
n
-1)
.
This matrix should be contained in one and only one process memory space (local operation).
Input Parameters
uplo
(global)
CHARACTER*1
.
Specifies whether the matrix sub (
A
) is upper or lower triangular.
=
'U'
: sub (
A
) is upper triangular
=
'L'
: sub (
A
) is lower triangular.
diag
(global)
CHARACTER*1
.
Specifies whether or not the matrix
A
is unit triangular.
=
'N'
: sub (
A
) is non-unit triangular
=
'U'
: sub (
A
) is unit triangular.
n
(global)
INTEGER
.
The number of rows and columns to be operated on, i.e., the order of the distributed submatrix
sub(
A
)
.
n
0
.
a
(local)
REAL
for
pstrti2
DOUBLE PRECISION
for
pdtrti2
COMPLEX
for
pctrti2
COMPLEX*16
for
pztrti2
.
Pointer into the local memory to an array,
size
(
lld_a
,
LOCc
(
ja
+
n
-1))
.
On entry, this array contains the local pieces of the triangular matrix sub(
A
).
If
uplo
=
'U'
n
-by-
n
upper triangular part of the matrix sub(
A
) contains the upper triangular part of the matrix, and the strictly lower triangular part of sub(
A
) is not referenced.
If
uplo
=
'L'
n
-by-
n
lower triangular part of the matrix sub(
A
) contains the lower triangular part of the matrix, and the strictly upper triangular part of sub(
A
) is not referenced. If
diag
=
'U'
, the diagonal elements of sub(
A
) are not referenced either and are assumed to be 1.
ia
,
ja
(global)
INTEGER
.
The row and column indices in the global matrix
A
indicating the first row and the first column of the sub(
A
), respectively.
desca
(global and local)
INTEGER
array of size
dlen_
. The array descriptor for the distributed matrix
A
.
Output Parameters
a
On exit, the (triangular) inverse of the original matrix, in the same storage format.
info
INTEGER
.
= 0
: successful exit
< 0
: if the
i
-th argument is an array and the
j
-th entry had an illegal value,
then
info
= - (
i
*100+
j
),
if the
i
-th argument is a scalar and had an illegal value,
then
info
= -
i
.