SRC/dtrcon.f(3)

NAME
SRC/dtrcon.f

SYNOPSIS

  Functions/Subroutines
subroutine dtrcon (norm, uplo, diag, n, a, lda, rcond, work, iwork, info)
DTRCON

Function/Subroutine Documentation

  subroutine dtrcon (character norm, character uplo, character diag, integer n, double precision, dimension( lda, * ) a, integer lda, double precision rcond, double precision, dimension( * ) work, integer, dimension( * ) iwork, integer info)

DTRCON

Purpose:

    !>
    !> DTRCON estimates the reciprocal of the condition number of a
    !> triangular matrix A, in either the 1-norm or the infinity-norm.
    !>
    !> The norm of A is computed and an estimate is obtained for
    !> norm(inv(A)), then the reciprocal of the condition number is
    !> computed as
    !>    RCOND = 1 / ( norm(A) * norm(inv(A)) ).
    !>

Parameters
    NORM

    !>          NORM is CHARACTER*1
    !>          Specifies whether the 1-norm condition number or the
    !>          infinity-norm condition number is required:
    !>          = '1' or 'O':  1-norm;
    !>          = 'I':         Infinity-norm.
    !>

    UPLO

    !>          UPLO is CHARACTER*1
    !>          = 'U':  A is upper triangular;
    !>          = 'L':  A is lower triangular.
    !>

    DIAG

    !>          DIAG is CHARACTER*1
    !>          = 'N':  A is non-unit triangular;
    !>          = 'U':  A is unit triangular.
    !>

    N

    !>          N is INTEGER
    !>          The order of the matrix A.  N >= 0.
    !>

    A

    !>          A is DOUBLE PRECISION array, dimension (LDA,N)
    !>          The triangular matrix A.  If UPLO = 'U', the leading N-by-N
    !>          upper triangular part of the array A contains the upper
    !>          triangular matrix, and the strictly lower triangular part of
    !>          A is not referenced.  If UPLO = 'L', the leading N-by-N lower
    !>          triangular part of the array A contains the lower triangular
    !>          matrix, and the strictly upper triangular part of A is not
    !>          referenced.  If DIAG = 'U', the diagonal elements of A are
    !>          also not referenced and are assumed to be 1.
    !>

    LDA

    !>          LDA is INTEGER
    !>          The leading dimension of the array A.  LDA >= max(1,N).
    !>

    RCOND

    !>          RCOND is DOUBLE PRECISION
    !>          The reciprocal of the condition number of the matrix A,
    !>          computed as RCOND = 1/(norm(A) * norm(inv(A))).
    !>

    WORK

    !>          WORK is DOUBLE PRECISION array, dimension (3*N)
    !>

    IWORK

    !>          IWORK is INTEGER array, dimension (N)
    !>

    INFO

    !>          INFO is INTEGER
    !>          = 0:  successful exit
    !>          < 0:  if INFO = -i, the i-th argument had an illegal value
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 135 of file dtrcon.f.

Author

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