zqrt17.f3

Usage

Functions/Subroutines

double precision function zqrt17 (trans, iresid, m, n, nrhs, a, lda, x, ldx, b, ldb, c, work, lwork)
ZQRT17

Function/Subroutine Documentation

double precision function zqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, complex16, dimension( lda, ) a, integer lda, complex16, dimension( ldx, ) x, integer ldx, complex16, dimension( ldb, ) b, integer ldb, complex16, dimension( ldb, ) c, complex*16, dimension( lwork ) work, integer lwork)

ZQRT17

Purpose:

!>
!> 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.
!>

Parameters

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 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 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 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 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 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 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).
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 151 of file zqrt17.f.