## Developer Reference

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

# ?sytri_rook

Computes the inverse of a symmetric matrix using
U
*
D
*
U
T
or
L
*
D
*
L
T
bounded Bunch-Kaufman factorization.

## Syntax

Include Files
• mkl.fi
,
lapack.f90
Description
The routine computes the inverse
inv(
A
)
of a symmetric matrix
A
. Before calling this routine, call
?sytrf_rook
to factorize
A
.
Input Parameters
uplo
CHARACTER*1
.
Must be
'U'
or
'L'
.
Indicates how the input matrix
A
has been factored:
If
uplo
=
'U'
, the array
a
stores the factorization
A
=
U*D*U
T
.
If
uplo
=
'L'
, the array
a
stores the factorization
A
=
L*D*L
T
.
n
INTEGER
.
The order of the matrix
A
;
n
0
.
a
,
work
REAL
for
ssytri_rook
DOUBLE PRECISION
for
dsytri_rook
COMPLEX
for
csytri_rook
DOUBLE COMPLEX
for
zsytri_rook
.
Arrays:
a
(size
lda
by *)
contains the factorization of the matrix
A
, as returned by
?sytrf_rook
.
The second dimension of
a
must be at least
max(1,
n
)
.
work
(*)
is a workspace array. The dimension of
work
must be at least
max(1,
n
)
.
lda
INTEGER
.
a
;
lda
max(1,
n
)
.
ipiv
INTEGER
.
Array, size at least
max(1,
n
)
.
The
ipiv
array, as returned by
?sytrf_rook
.
Output Parameters
a
Overwritten by the
n
-by-
n
matrix
inv(
A
)
. If
uplo
=
'U'
, the upper triangular part of the inverse is formed and the part of
a
below the diagonal is not referenced; if