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# ssytri2.f

ssytri2.f −

## SYNOPSIS

Functions/Subroutines

subroutine ssytri2 (UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO)
SSYTRI2

## Function/Subroutine Documentation

subroutine ssytri2 (characterUPLO, integerN, real, dimension( lda, * )A, integerLDA, integer, dimension( * )IPIV, real, dimension( * )WORK, integerLWORK, integerINFO)
SSYTRI2

Purpose:

SSYTRI2 computes the inverse of a REAL symmetric indefinite matrix
A using the factorization A = U*D*U**T or A = L*D*L**T computed by
SSYTRF. SSYTRI2 sets the LEADING DIMENSION of the workspace
before calling SSYTRI2X that actually computes the inverse.

Parameters:

UPLO

UPLO is CHARACTER*1
Specifies whether the details of the factorization are stored
as an upper or lower triangular matrix.
= ’U’: Upper triangular, form is A = U*D*U**T;
= ’L’: Lower triangular, form is A = L*D*L**T.

N

N is INTEGER
The order of the matrix A. N >= 0.

A

A is REAL array, dimension (LDA,N)
On entry, the NB diagonal matrix D and the multipliers
used to obtain the factor U or L as computed by SSYTRF.

On exit, if INFO = 0, the (symmetric) inverse of the original
matrix. If UPLO = ’U’, the upper triangular part of the
inverse is formed and the part of A below the diagonal is not
referenced; if UPLO = ’L’ the lower triangular part of the
inverse is formed and the part of A above the diagonal is
not referenced.

LDA

LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,N).

IPIV

IPIV is INTEGER array, dimension (N)
Details of the interchanges and the NB structure of D
as determined by SSYTRF.

WORK

WORK is REAL array, dimension (N+NB+1)*(NB+3)

LWORK

LWORK is INTEGER
The dimension of the array WORK.
WORK is size >= (N+NB+1)*(NB+3)
If LDWORK = -1, then a workspace query is assumed; the routine
calculates:
- the optimal size of the WORK array, returns
this value as the first entry of the WORK array,
- and no error message related to LDWORK is issued by XERBLA.

INFO

INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
inverse could not be computed.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 128 of file ssytri2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

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