## Developer Reference

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

# ?sytri2

Computes the inverse of a symmetric indefinite matrix through
setting the leading dimension of the workspace
and calling
?sytri2x
.

## Syntax

Include Files
• mkl.fi
,
lapack.f90
Description
The routine computes the inverse
inv(
A
)
of a symmetric indefinite matrix
A
using the factorization
A
=
U*D*U
T
or
A
=
L*D*L
T
computed by
?sytrf
.
The
?sytri2
routine
sets the leading dimension of the workspace
before calling
?sytri2x
that actually computes the inverse.
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
ssytri2
DOUBLE PRECISION
for
dsytri2
COMPLEX
for
csytri2
DOUBLE COMPLEX
for
zsytri2
Array
a
(size
lda
by
n
)
contains the block diagonal matrix
D
and the multipliers used to obtain the factor
U
or
L
as returned by
?sytrf
.
The second dimension of
a
must be at least
max(1,
n
)
.
work
is a workspace array of
(
n
+
nb
+1)*(
nb
+3)
dimension.
lda
INTEGER
.
a
;
lda
max(1,
n
)
.
ipiv
INTEGER
.
Array, size at least
max(1,
n
)
.
Details of the interchanges and the block structure of
D
as returned by
?sytrf
.
lwork
INTEGER
.
The dimension of the
work
array.
lwork
(
n
+
nb
+1)*(
nb
+3)