TESTING/LIN/dqrt14.f(3)

NAME
TESTING/LIN/dqrt14.f

SYNOPSIS

  Functions/Subroutines
double precision function dqrt14 (trans, m, n, nrhs, a, lda, x, ldx, work, lwork)
DQRT14

Function/Subroutine Documentation

  double precision function dqrt14 (character trans, integer m, integer n, integer nrhs, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( lwork ) work, integer lwork)

DQRT14

Purpose:

     DQRT14 checks whether X is in the row space of A or A'.  It does so
     by scaling both X and A such that their norms are in the range
     [sqrt(eps), 1/sqrt(eps)], then computing a QR factorization of [A,X]
     (if TRANS = 'T') or an LQ factorization of [A',X]' (if TRANS = 'N'),
     and returning the norm of the trailing triangle, scaled by
     MAX(M,N,NRHS)*eps.

Parameters
    TRANS

              TRANS is CHARACTER*1
              = 'N':  No transpose, check for X in the row space of A
              = 'T':  Transpose, check for X in the row space of A'.

    M

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

    N

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

    NRHS

              NRHS is INTEGER
              The number of right hand sides, i.e., the number of columns
              of X.

    A

              A is DOUBLE PRECISION array, dimension (LDA,N)
              The M-by-N matrix A.

    LDA

              LDA is INTEGER
              The leading dimension of the array A.

    X

              X is DOUBLE PRECISION array, dimension (LDX,NRHS)
              If TRANS = 'N', the N-by-NRHS matrix X.
              IF TRANS = 'T', the M-by-NRHS matrix X.

    LDX

              LDX is INTEGER
              The leading dimension of the array X.

    WORK

              WORK is DOUBLE PRECISION array dimension (LWORK)

    LWORK

              LWORK is INTEGER
              length of workspace array required
              If TRANS = 'N', LWORK >= (M+NRHS)*(N+2);
              if TRANS = 'T', LWORK >= (N+NRHS)*(M+2).

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 114 of file dqrt14.f.

Author

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