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LAPACK
3.7.0
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 | ||
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DQRT17
DQRT17 computes the ratio || R'*op(A) ||/(||A||*alpha*max(M,N,NRHS)*eps) where R = op(A)*X - B, op(A) is A or A', and alpha = ||B|| if IRESID = 1 (zero-residual problem) alpha = ||R|| if IRESID = 2 (otherwise).
[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'. |
[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). |
Definition at line 152 of file dqrt17.f.