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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