SRC/dsytri2.f(3)

NAME
SRC/dsytri2.f

SYNOPSIS

  Functions/Subroutines
subroutine dsytri2 (uplo, n, a, lda, ipiv, work, lwork, info)
DSYTRI2

Function/Subroutine Documentation

  subroutine dsytri2 (character uplo, integer n, double precision, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, double precision, dimension( * ) work, integer lwork, integer info)

DSYTRI2

Purpose:

    !>
    !> DSYTRI2 computes the inverse of a DOUBLE PRECISION symmetric indefinite matrix
    !> A using the factorization A = U*D*U**T or A = L*D*L**T computed by
    !> DSYTRF. DSYTRI2 sets the LEADING DIMENSION of the workspace
    !> before calling DSYTRI2X 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 DOUBLE PRECISION 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 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 block structure of D
    !>          as determined by DSYTRF.
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
    !>

    LWORK

    !>          LWORK is INTEGER
    !>          The dimension of the array WORK.
    !>          If N = 0, LWORK >= 1, else LWORK >= (N+NB+1)*(NB+3).
    !>          If LWORK = -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 LWORK 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.

Definition at line 126 of file dsytri2.f.

Author

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