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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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| double precision function dqrt17 | ( | character | trans, |
| integer | iresid, | ||
| integer | m, | ||
| integer | n, | ||
| integer | nrhs, | ||
| double precision, dimension( lda, * ) | a, | ||
| integer | lda, | ||
| double precision, dimension( ldx, * ) | x, | ||
| integer | ldx, | ||
| double precision, dimension( ldb, * ) | b, | ||
| integer | ldb, | ||
| double precision, dimension( ldb, * ) | c, | ||
| double precision, dimension( lwork ) | work, | ||
| integer | lwork | ||
| ) |
DQRT17
DQRT17 computes the ratio
norm(R**T * op(A)) / ( norm(A) * alpha * max(M,N,NRHS) * EPS ),
where R = B - op(A)*X, op(A) is A or A**T, 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. | [in] | TRANS | TRANS is CHARACTER*1
Specifies whether or not the transpose of A is used.
= 'N': No transpose, op(A) = A.
= 'T': Transpose, op(A) = A**T. |
| [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 = 'T', 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 = 'T', 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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.
If TRANS = 'N', LDX >= N.
If TRANS = 'T', LDX >= M. |
| [in] | B | B is DOUBLE PRECISION array, dimension (LDB,NRHS)
If TRANS = 'N', the m-by-nrhs matrix B.
If TRANS = 'T', 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 = 'T', LDB >= N. |
| [out] | C | C is DOUBLE PRECISION array, dimension (LDB,NRHS) |
| [out] | WORK | WORK is DOUBLE PRECISION array, dimension (LWORK) |
| [in] | LWORK | LWORK is INTEGER
The length of the array WORK. LWORK >= NRHS*(M+N). |
1.9.7