ZQRT17 computes the ratio


    norm(R**H * op(A)) / ( norm(A) * alpha * max(M,N,NRHS) * EPS ),


 where R = B - op(A)*X, op(A) is A or A**H, 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.

TRANS

          TRANS is CHARACTER*1


          Specifies whether or not the transpose of A is used.


          = 'N':  No transpose, op(A) = A.


          = 'C':  Conjugate transpose, op(A) = A**H.

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 = 'C', 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 = 'C', 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 COMPLEX*16 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 COMPLEX*16 array, dimension (LDX,NRHS)


          If TRANS = 'N', the n-by-nrhs matrix X.


          If TRANS = 'C', the m-by-nrhs matrix X.

LDX

          LDX is INTEGER


          The leading dimension of the array X.


          If TRANS = 'N', LDX >= N.


          If TRANS = 'C', LDX >= M.

B

          B is COMPLEX*16 array, dimension (LDB,NRHS)


          If TRANS = 'N', the m-by-nrhs matrix B.


          If TRANS = 'C', the n-by-nrhs matrix B.

LDB

          LDB is INTEGER


          The leading dimension of the array B.


          If TRANS = 'N', LDB >= M.


          If TRANS = 'C', LDB >= N.

C

          C is COMPLEX*16 array, dimension (LDB,NRHS)

WORK

          WORK is COMPLEX*16 array, dimension (LWORK)

LWORK

          LWORK is INTEGER


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

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.