TESTING/EIG/dort01.f(3)

NAME
TESTING/EIG/dort01.f

SYNOPSIS

  Functions/Subroutines
subroutine dort01 (rowcol, m, n, u, ldu, work, lwork, resid)
DORT01

Function/Subroutine Documentation

  subroutine dort01 (character rowcol, integer m, integer n, double precision, dimension( ldu, * ) u, integer ldu, double precision, dimension( * ) work, integer lwork, double precision resid)

DORT01

Purpose:

     DORT01 checks that the matrix U is orthogonal by computing the ratio
        RESID = norm( I - U*U' ) / ( n * EPS ), if ROWCOL = 'R',
     or
        RESID = norm( I - U'*U ) / ( m * EPS ), if ROWCOL = 'C'.
     Alternatively, if there isn't sufficient workspace to form
     I - U*U' or I - U'*U, the ratio is computed as
        RESID = abs( I - U*U' ) / ( n * EPS ), if ROWCOL = 'R',
     or
        RESID = abs( I - U'*U ) / ( m * EPS ), if ROWCOL = 'C'.
     where EPS is the machine precision.  ROWCOL is used only if m = n;
     if m > n, ROWCOL is assumed to be 'C', and if m < n, ROWCOL is
     assumed to be 'R'.

Parameters
    ROWCOL

              ROWCOL is CHARACTER
              Specifies whether the rows or columns of U should be checked
              for orthogonality.  Used only if M = N.
              = 'R':  Check for orthogonal rows of U
              = 'C':  Check for orthogonal columns of U

    M

              M is INTEGER
              The number of rows of the matrix U.

    N

              N is INTEGER
              The number of columns of the matrix U.

    U

              U is DOUBLE PRECISION array, dimension (LDU,N)
              The orthogonal matrix U.  U is checked for orthogonal columns
              if m > n or if m = n and ROWCOL = 'C'.  U is checked for
              orthogonal rows if m < n or if m = n and ROWCOL = 'R'.

    LDU

              LDU is INTEGER
              The leading dimension of the array U.  LDU >= max(1,M).

    WORK

              WORK is DOUBLE PRECISION array, dimension (LWORK)

    LWORK

              LWORK is INTEGER
              The length of the array WORK.  For best performance, LWORK
              should be at least N*(N+1) if ROWCOL = 'C' or M*(M+1) if
              ROWCOL = 'R', but the test will be done even if LWORK is 0.

    RESID

              RESID is DOUBLE PRECISION
              RESID = norm( I - U * U' ) / ( n * EPS ), if ROWCOL = 'R', or
              RESID = norm( I - U' * U ) / ( m * EPS ), if ROWCOL = 'C'.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 115 of file dort01.f.

Author

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