zqrt14.f - Man Page

double precision function zqrt14 (trans, m, n, nrhs, a, lda, x, ldx, work, lwork)
ZQRT14

ZQRT14

Purpose:

 ZQRT14 checks whether X is in the row space of A or A'.  It does so
 by scaling both X and A such that their norms are in the range
 [sqrt(eps), 1/sqrt(eps)], then computing a QR factorization of [A,X]
 (if TRANS = 'C') or an LQ factorization of [A',X]' (if TRANS = 'N'),
 and returning the norm of the trailing triangle, scaled by
 MAX(M,N,NRHS)*eps.

Parameters

TRANS

          TRANS is CHARACTER*1
          = 'N':  No transpose, check for X in the row space of A
          = 'C':  Conjugate transpose, check for X in row space of A'.

M

          M is INTEGER
          The number of rows of the matrix A.

N

          N is INTEGER
          The number of columns of the matrix A.

NRHS

          NRHS is INTEGER
          The number of right hand sides, i.e., the number of columns
          of X.

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.

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.

WORK

          WORK is COMPLEX*16 array dimension (LWORK)

LWORK

          LWORK is INTEGER
          length of workspace array required
          If TRANS = 'N', LWORK >= (M+NRHS)*(N+2);
          if TRANS = 'C', LWORK >= (N+NRHS)*(M+2).

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 114 of file zqrt14.f.