SRC/dsytri2x.f(3)

NAME
SRC/dsytri2x.f

SYNOPSIS

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

Function/Subroutine Documentation

  subroutine dsytri2x (character uplo, integer n, double precision, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, double precision, dimension( n+nb+1,* ) work, integer nb, integer info)

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.

Author

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