dsytri2x.f - Man Page

subroutine dsytri2x (uplo, n, a, lda, ipiv, work, nb, info)
DSYTRI2X

DSYTRI2X  

Purpose:

 DSYTRI2X 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
 DSYTRF.

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 DOUBLE PRECISION array, dimension (LDA,N)
          On entry, the NNB diagonal matrix D and the multipliers
          used to obtain the factor U or L as computed by DSYTRF.

          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 NNB structure of D
          as determined by DSYTRF.

WORK

          WORK is DOUBLE PRECISION array, dimension (N+NB+1,NB+3)

NB

          NB is INTEGER
          Block size

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.

Definition at line 119 of file dsytri2x.f.