SRC/dsptri.f(3)

NAME
SRC/dsptri.f

SYNOPSIS

  Functions/Subroutines
subroutine dsptri (uplo, n, ap, ipiv, work, info)
DSPTRI

Function/Subroutine Documentation

  subroutine dsptri (character uplo, integer n, double precision, dimension( * ) ap, integer, dimension( * ) ipiv, double precision, dimension( * ) work, integer info)

DSPTRI

Purpose:

    !>
    !> DSPTRI computes the inverse of a real symmetric indefinite matrix
    !> A in packed storage using the factorization A = U*D*U**T or
    !> A = L*D*L**T computed by DSPTRF.
    !>

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.
    !>

    AP

    !>          AP is DOUBLE PRECISION array, dimension (N*(N+1)/2)
    !>          On entry, the block diagonal matrix D and the multipliers
    !>          used to obtain the factor U or L as computed by DSPTRF,
    !>          stored as a packed triangular matrix.
    !>
    !>          On exit, if INFO = 0, the (symmetric) inverse of the original
    !>          matrix, stored as a packed triangular matrix. The j-th column
    !>          of inv(A) is stored in the array AP as follows:
    !>          if UPLO = 'U', AP(i + (j-1)*j/2) = inv(A)(i,j) for 1<=i<=j;
    !>          if UPLO = 'L',
    !>             AP(i + (j-1)*(2n-j)/2) = inv(A)(i,j) for j<=i<=n.
    !>

    IPIV

    !>          IPIV is INTEGER array, dimension (N)
    !>          Details of the interchanges and the block structure of D
    !>          as determined by DSPTRF.
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (N)
    !>

    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 108 of file dsptri.f.

Author

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