LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
Loading...
Searching...
No Matches

◆ zqrt17()

double precision function zqrt17 ( character  trans,
integer  iresid,
integer  m,
integer  n,
integer  nrhs,
complex*16, dimension( lda, * )  a,
integer  lda,
complex*16, dimension( ldx, * )  x,
integer  ldx,
complex*16, dimension( ldb, * )  b,
integer  ldb,
complex*16, 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
[in]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.
[in]IRESID
          IRESID is INTEGER
          IRESID = 1 indicates zero-residual problem.
          IRESID = 2 indicates non-zero residual.
[in]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.
[in]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.
[in]NRHS
          NRHS is INTEGER
          The number of columns of the matrices X and B.
[in]A
          A is COMPLEX*16 array, dimension (LDA,N)
          The m-by-n matrix A.
[in]LDA
          LDA is INTEGER
          The leading dimension of the array A. LDA >= M.
[in]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.
[in]LDX
          LDX is INTEGER
          The leading dimension of the array X.
          If TRANS = 'N', LDX >= N.
          If TRANS = 'C', LDX >= M.
[in]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.
[in]LDB
          LDB is INTEGER
          The leading dimension of the array B.
          If TRANS = 'N', LDB >= M.
          If TRANS = 'C', LDB >= N.
[out]C
          C is COMPLEX*16 array, dimension (LDB,NRHS)
[out]WORK
          WORK is COMPLEX*16 array, dimension (LWORK)
[in]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.