Contents

# ?pftri

Computes the inverse of a symmetric (Hermitian) positive-definite matrix in RFP format using the Cholesky factorization.

## Syntax

Include Files
• mkl.h
Description
The routine computes the inverse
inv(
A
)
of a symmetric positive definite or, for complex data, Hermitian positive-definite matrix
A
using the Cholesky factorization:
 A = UT*U for real data, A = UH*U for complex data if uplo='U' A = L*LT for real data, A = L*LH for complex data if uplo='L'
Before calling this routine, call
?pftrf
to factorize
A
.
The matrix
A
is in the Rectangular Full Packed (RFP) format. For the description of the RFP format, see Matrix Storage Schemes.
Input Parameters
matrix_layout
Specifies whether matrix storage layout is row major (
LAPACK_ROW_MAJOR
) or column major (
LAPACK_COL_MAJOR
).
transr
Must be
'N'
,
'T'
(for real data) or
'C'
(for complex data).
If
transr
=
'N'
, the Normal
transr
of RFP
U
(if
uplo
=
'U'
) or
L
(if
uplo
=
'L'
) is stored.
If
transr
=
'T'
, the Transpose
transr
of RFP
U
(if
uplo
=
'U'
) or
L
(if
uplo
=
'L'
is stored.
If
transr
=
'C'
, the Conjugate-Transpose
transr
of RFP
U
(if
uplo
=
'U'
) or
L
(if
uplo
=
'L'
is stored.
uplo
Must be
'U'
or
'L'
.
Indicates how the input matrix
A
has been factored:
If
uplo
=
'U'
,
A
=
U
T
*
U
for real data or
A
=
U
H
*
U
for complex data, and
U
is stored.
If
uplo
=
'L'
,
A
=
L
*
L
T
for real data or
A
=
L
*
L
H
for complex data, and
L
is stored.
n
The order of the matrix
A
;
n
0.
a
Array, size
(
n
*(
n
+1)/2)
. The array
a
contains the factor
U
or
L
matrix
A
in the RFP format.
Output Parameters
a
The symmetric/Hermitian inverse of the original matrix in the same storage format.
Return Values
This function returns a value
info
.
If
info
=0
, the execution is successful.
If
info
=
-i
, parameter
i
If
info
=
i
, the
(
i
,
i
)
element of the factor
U
or
L
is zero, and the inverse could not be computed.

#### Product and Performance Information

1

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