TESTING/LIN/sqrt14.f(3)

NAME
TESTING/LIN/sqrt14.f

SYNOPSIS

  Functions/Subroutines
real function sqrt14 (trans, m, n, nrhs, a, lda, x, ldx, work, lwork)
SQRT14

Function/Subroutine Documentation

  real function sqrt14 (character trans, integer m, integer n, integer nrhs, real, dimension( lda, * ) a, integer lda, real, dimension( ldx, * ) x, integer ldx, real, dimension( lwork ) work, integer lwork)

SQRT14

Purpose:

     SQRT14 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 REAL array, dimension (LDA,N)
              The M-by-N matrix A.

    LDA

              LDA is INTEGER
              The leading dimension of the array A.

    X

              X is REAL 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 REAL 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 sqrt14.f.

Author

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