TESTING/LIN/sqrt14.f(3) | Library Functions Manual | TESTING/LIN/sqrt14.f(3) |
NAME
TESTING/LIN/sqrt14.f
SYNOPSIS
Functions/Subroutines
real function sqrt14 (trans, m, n, nrhs, a, lda, x, ldx,
work, lwork)
SQRT14
Function/Subroutine Documentation
real function sqrt14 (character trans, integer m, integer n, integer nrhs, real, dimension( lda, * ) a, integer lda, real, dimension( ldx, * ) x, integer ldx, real, dimension( lwork ) work, integer lwork)
SQRT14
Purpose:
SQRT14 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 = 'T') 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 = 'T': Transpose, check for X in the 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 REAL array, dimension (LDA,N) The M-by-N matrix A.
LDA
LDA is INTEGER The leading dimension of the array A.
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.
WORK
WORK is REAL array dimension (LWORK)
LWORK
LWORK is INTEGER length of workspace array required If TRANS = 'N', LWORK >= (M+NRHS)*(N+2); if TRANS = 'T', 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 sqrt14.f.
Author
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