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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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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
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.
[in] | 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'. |
[in] | M | M is INTEGER The number of rows of the matrix A. |
[in] | N | N is INTEGER The number of columns of the matrix A. |
[in] | NRHS | NRHS is INTEGER The number of right hand sides, i.e., the number of columns of X. |
[in] | A | A is REAL array, dimension (LDA,N) The M-by-N matrix A. |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. |
[in] | 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. |
[in] | LDX | LDX is INTEGER The leading dimension of the array X. |
[out] | WORK | WORK is REAL array dimension (LWORK) |
[in] | 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). |
Definition at line 118 of file sqrt14.f.