NAME
SSYTRI - 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
SYNOPSIS
- SUBROUTINE SSYTRI(
-
UPLO, N, A, LDA, IPIV, WORK, INFO )
- CHARACTER
-
UPLO
- INTEGER
-
INFO, LDA, N
- INTEGER
-
IPIV( * )
- REAL
-
A( LDA, * ), WORK( * )
PURPOSE
SSYTRI 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.
ARGUMENTS
- UPLO (input) 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 (input) INTEGER
-
The order of the matrix A. N >= 0.
- A (input/output) REAL array, dimension (LDA,N)
-
On entry, the block 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 (input) INTEGER
-
The leading dimension of the array A. LDA >= max(1,N).
- IPIV (input) INTEGER array, dimension (N)
-
Details of the interchanges and the block structure of D as determined by SSYTRF.
- WORK (workspace) REAL array, dimension (N)
- INFO (output) 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.