TESTING/LIN/sqrt17.f(3)

NAME
TESTING/LIN/sqrt17.f

SYNOPSIS

  Functions/Subroutines
real function sqrt17 (trans, iresid, m, n, nrhs, a, lda, x, ldx, b, ldb, c, work, lwork)
SQRT17

Function/Subroutine Documentation

  real function sqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, real, dimension( lda, * ) a, integer lda, real, dimension( ldx, * ) x, integer ldx, real, dimension( ldb, * ) b, integer ldb, real, dimension( ldb, * ) c, real, dimension( lwork ) work, integer lwork)

SQRT17

Purpose:

    !>
    !> SQRT17 computes the ratio
    !>
    !>    norm(R**T * op(A)) / ( norm(A) * alpha * max(M,N,NRHS) * EPS ),
    !>
    !> where R = B - op(A)*X, op(A) is A or A**T, depending on TRANS, EPS
    !> is the machine epsilon, and
    !>
    !>    alpha = norm(B) if IRESID = 1 (zero-residual problem)
    !>    alpha = norm(R) if IRESID = 2 (otherwise).
    !>
    !> The norm used is the 1-norm.
    !>

Parameters
    TRANS

    !>          TRANS is CHARACTER*1
    !>          Specifies whether or not the transpose of A is used.
    !>          = 'N':  No transpose, op(A) = A.
    !>          = 'T':  Transpose, op(A) = A**T.
    !>

    IRESID

    !>          IRESID is INTEGER
    !>          IRESID = 1 indicates zero-residual problem.
    !>          IRESID = 2 indicates non-zero residual.
    !>

    M

    !>          M is INTEGER
    !>          The number of rows of the matrix A.
    !>          If TRANS = 'N', the number of rows of the matrix B.
    !>          If TRANS = 'T', the number of rows of the matrix X.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix  A.
    !>          If TRANS = 'N', the number of rows of the matrix X.
    !>          If TRANS = 'T', the number of rows of the matrix B.
    !>

    NRHS

    !>          NRHS is INTEGER
    !>          The number of columns of the matrices X and B.
    !>

    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. LDA >= M.
    !>

    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.
    !>          If TRANS = 'N', LDX >= N.
    !>          If TRANS = 'T', LDX >= M.
    !>

    B

    !>          B is REAL array, dimension (LDB,NRHS)
    !>          If TRANS = 'N', the m-by-nrhs matrix B.
    !>          If TRANS = 'T', the n-by-nrhs matrix B.
    !>

    LDB

    !>          LDB is INTEGER
    !>          The leading dimension of the array B.
    !>          If TRANS = 'N', LDB >= M.
    !>          If TRANS = 'T', LDB >= N.
    !>

    C

    !>          C is REAL array, dimension (LDB,NRHS)
    !>

    WORK

    !>          WORK is REAL array, dimension (LWORK)
    !>

    LWORK

    !>          LWORK is INTEGER
    !>          The length of the array WORK.  LWORK >= NRHS*(M+N).
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 151 of file sqrt17.f.

Author

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