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410 lines
11 KiB
410 lines
11 KiB
*> \brief \b SLAMSWLQ
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE SLAMSWLQ( SIDE, TRANS, M, N, K, MB, NB, A, LDA, T,
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* $ LDT, C, LDC, WORK, LWORK, INFO )
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*
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*
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* .. Scalar Arguments ..
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* CHARACTER SIDE, TRANS
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* INTEGER INFO, LDA, M, N, K, MB, NB, LDT, LWORK, LDC
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* ..
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* .. Array Arguments ..
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* DOUBLE A( LDA, * ), WORK( * ), C(LDC, * ),
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* $ T( LDT, * )
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> SLAMSWLQ overwrites the general real M-by-N matrix C with
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*>
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*>
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*> SIDE = 'L' SIDE = 'R'
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*> TRANS = 'N': Q * C C * Q
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*> TRANS = 'T': Q**T * C C * Q**T
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*> where Q is a real orthogonal matrix defined as the product of blocked
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*> elementary reflectors computed by short wide LQ
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*> factorization (SLASWLQ)
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] SIDE
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*> \verbatim
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*> SIDE is CHARACTER*1
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*> = 'L': apply Q or Q**T from the Left;
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*> = 'R': apply Q or Q**T from the Right.
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*> \endverbatim
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*>
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*> \param[in] TRANS
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*> \verbatim
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*> TRANS is CHARACTER*1
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*> = 'N': No transpose, apply Q;
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*> = 'T': Transpose, apply Q**T.
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*> \endverbatim
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*>
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*> \param[in] M
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*> \verbatim
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*> M is INTEGER
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*> The number of rows of the matrix C. M >=0.
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*> \endverbatim
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*>
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of columns of the matrix C. N >= 0.
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*> \endverbatim
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*>
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*> \param[in] K
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*> \verbatim
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*> K is INTEGER
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*> The number of elementary reflectors whose product defines
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*> the matrix Q.
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*> M >= K >= 0;
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*>
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*> \endverbatim
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*> \param[in] MB
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*> \verbatim
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*> MB is INTEGER
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*> The row block size to be used in the blocked LQ.
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*> M >= MB >= 1
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*> \endverbatim
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*>
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*> \param[in] NB
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*> \verbatim
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*> NB is INTEGER
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*> The column block size to be used in the blocked LQ.
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*> NB > M.
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*> \endverbatim
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*>
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*> \param[in] A
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*> \verbatim
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*> A is REAL array, dimension
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*> (LDA,M) if SIDE = 'L',
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*> (LDA,N) if SIDE = 'R'
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*> The i-th row must contain the vector which defines the blocked
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*> elementary reflector H(i), for i = 1,2,...,k, as returned by
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*> SLASWLQ in the first k rows of its array argument A.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A. LDA >= max(1,K).
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*> \endverbatim
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*>
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*> \param[in] T
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*> \verbatim
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*> T is REAL array, dimension
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*> ( M * Number of blocks(CEIL(N-K/NB-K)),
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*> The blocked upper triangular block reflectors stored in compact form
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*> as a sequence of upper triangular blocks. See below
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*> for further details.
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*> \endverbatim
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*>
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*> \param[in] LDT
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*> \verbatim
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*> LDT is INTEGER
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*> The leading dimension of the array T. LDT >= MB.
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*> \endverbatim
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*>
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*> \param[in,out] C
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*> \verbatim
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*> C is REAL array, dimension (LDC,N)
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*> On entry, the M-by-N matrix C.
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*> On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
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*> \endverbatim
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*>
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*> \param[in] LDC
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*> \verbatim
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*> LDC is INTEGER
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*> The leading dimension of the array C. LDC >= max(1,M).
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*> \endverbatim
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*>
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*> \param[out] WORK
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*> \verbatim
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*> (workspace) REAL array, dimension (MAX(1,LWORK))
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*> \endverbatim
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*>
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*> \param[in] LWORK
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*> \verbatim
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*> LWORK is INTEGER
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*> The dimension of the array WORK.
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*> If SIDE = 'L', LWORK >= max(1,NB) * MB;
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*> if SIDE = 'R', LWORK >= max(1,M) * MB.
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*> If LWORK = -1, then a workspace query is assumed; the routine
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*> only calculates the optimal size of the WORK array, returns
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*> this value as the first entry of the WORK array, and no error
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*> message related to LWORK is issued by XERBLA.
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*> \endverbatim
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*>
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*> \param[out] INFO
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*> \verbatim
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*> INFO is INTEGER
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*> = 0: successful exit
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*> < 0: if INFO = -i, the i-th argument had an illegal value
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \par Further Details:
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* =====================
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*>
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*> \verbatim
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*> Short-Wide LQ (SWLQ) performs LQ by a sequence of orthogonal transformations,
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*> representing Q as a product of other orthogonal matrices
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*> Q = Q(1) * Q(2) * . . . * Q(k)
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*> where each Q(i) zeros out upper diagonal entries of a block of NB rows of A:
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*> Q(1) zeros out the upper diagonal entries of rows 1:NB of A
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*> Q(2) zeros out the bottom MB-N rows of rows [1:M,NB+1:2*NB-M] of A
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*> Q(3) zeros out the bottom MB-N rows of rows [1:M,2*NB-M+1:3*NB-2*M] of A
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*> . . .
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*>
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*> Q(1) is computed by GELQT, which represents Q(1) by Householder vectors
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*> stored under the diagonal of rows 1:MB of A, and by upper triangular
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*> block reflectors, stored in array T(1:LDT,1:N).
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*> For more information see Further Details in GELQT.
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*>
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*> Q(i) for i>1 is computed by TPLQT, which represents Q(i) by Householder vectors
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*> stored in columns [(i-1)*(NB-M)+M+1:i*(NB-M)+M] of A, and by upper triangular
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*> block reflectors, stored in array T(1:LDT,(i-1)*M+1:i*M).
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*> The last Q(k) may use fewer rows.
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*> For more information see Further Details in TPLQT.
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*>
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*> For more details of the overall algorithm, see the description of
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*> Sequential TSQR in Section 2.2 of [1].
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*>
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*> [1] “Communication-Optimal Parallel and Sequential QR and LU Factorizations,”
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*> J. Demmel, L. Grigori, M. Hoemmen, J. Langou,
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*> SIAM J. Sci. Comput, vol. 34, no. 1, 2012
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*> \endverbatim
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*>
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* =====================================================================
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SUBROUTINE SLAMSWLQ( SIDE, TRANS, M, N, K, MB, NB, A, LDA, T,
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$ LDT, C, LDC, WORK, LWORK, INFO )
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*
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* -- LAPACK computational routine --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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CHARACTER SIDE, TRANS
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INTEGER INFO, LDA, M, N, K, MB, NB, LDT, LWORK, LDC
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* ..
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* .. Array Arguments ..
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REAL A( LDA, * ), WORK( * ), C(LDC, * ),
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$ T( LDT, * )
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* ..
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*
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* =====================================================================
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*
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* ..
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* .. Local Scalars ..
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LOGICAL LEFT, RIGHT, TRAN, NOTRAN, LQUERY
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INTEGER I, II, KK, LW, CTR
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* .. External Subroutines ..
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EXTERNAL STPMLQT, SGEMLQT, XERBLA
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* ..
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* .. Executable Statements ..
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*
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* Test the input arguments
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*
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LQUERY = LWORK.LT.0
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NOTRAN = LSAME( TRANS, 'N' )
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TRAN = LSAME( TRANS, 'T' )
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LEFT = LSAME( SIDE, 'L' )
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RIGHT = LSAME( SIDE, 'R' )
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IF (LEFT) THEN
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LW = N * MB
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ELSE
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LW = M * MB
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END IF
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*
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INFO = 0
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IF( .NOT.LEFT .AND. .NOT.RIGHT ) THEN
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INFO = -1
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ELSE IF( .NOT.TRAN .AND. .NOT.NOTRAN ) THEN
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INFO = -2
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ELSE IF( K.LT.0 ) THEN
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INFO = -5
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ELSE IF( M.LT.K ) THEN
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INFO = -3
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ELSE IF( N.LT.0 ) THEN
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INFO = -4
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ELSE IF( K.LT.MB .OR. MB.LT.1) THEN
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INFO = -6
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ELSE IF( LDA.LT.MAX( 1, K ) ) THEN
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INFO = -9
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ELSE IF( LDT.LT.MAX( 1, MB) ) THEN
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INFO = -11
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ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
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INFO = -13
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ELSE IF(( LWORK.LT.MAX(1,LW)).AND.(.NOT.LQUERY)) THEN
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INFO = -15
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END IF
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*
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'SLAMSWLQ', -INFO )
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WORK(1) = LW
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RETURN
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ELSE IF (LQUERY) THEN
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WORK(1) = LW
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RETURN
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END IF
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*
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* Quick return if possible
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*
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IF( MIN(M,N,K).EQ.0 ) THEN
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RETURN
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END IF
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*
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IF((NB.LE.K).OR.(NB.GE.MAX(M,N,K))) THEN
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CALL SGEMLQT( SIDE, TRANS, M, N, K, MB, A, LDA,
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$ T, LDT, C, LDC, WORK, INFO)
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RETURN
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END IF
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*
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IF(LEFT.AND.TRAN) THEN
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*
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* Multiply Q to the last block of C
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*
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KK = MOD((M-K),(NB-K))
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CTR = (M-K)/(NB-K)
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*
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IF (KK.GT.0) THEN
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II=M-KK+1
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CALL STPMLQT('L','T',KK , N, K, 0, MB, A(1,II), LDA,
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$ T(1,CTR*K+1), LDT, C(1,1), LDC,
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$ C(II,1), LDC, WORK, INFO )
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ELSE
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II=M+1
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END IF
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*
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DO I=II-(NB-K),NB+1,-(NB-K)
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*
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* Multiply Q to the current block of C (1:M,I:I+NB)
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*
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CTR = CTR - 1
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CALL STPMLQT('L','T',NB-K , N, K, 0,MB, A(1,I), LDA,
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$ T(1,CTR*K+1),LDT, C(1,1), LDC,
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$ C(I,1), LDC, WORK, INFO )
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END DO
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*
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* Multiply Q to the first block of C (1:M,1:NB)
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*
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CALL SGEMLQT('L','T',NB , N, K, MB, A(1,1), LDA, T
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$ ,LDT ,C(1,1), LDC, WORK, INFO )
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*
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ELSE IF (LEFT.AND.NOTRAN) THEN
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*
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* Multiply Q to the first block of C
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*
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KK = MOD((M-K),(NB-K))
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II=M-KK+1
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CTR = 1
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CALL SGEMLQT('L','N',NB , N, K, MB, A(1,1), LDA, T
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$ ,LDT ,C(1,1), LDC, WORK, INFO )
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*
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DO I=NB+1,II-NB+K,(NB-K)
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*
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* Multiply Q to the current block of C (I:I+NB,1:N)
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*
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CALL STPMLQT('L','N',NB-K , N, K, 0,MB, A(1,I), LDA,
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$ T(1,CTR * K+1), LDT, C(1,1), LDC,
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$ C(I,1), LDC, WORK, INFO )
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CTR = CTR + 1
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*
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END DO
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IF(II.LE.M) THEN
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*
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* Multiply Q to the last block of C
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*
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CALL STPMLQT('L','N',KK , N, K, 0, MB, A(1,II), LDA,
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$ T(1,CTR*K+1), LDT, C(1,1), LDC,
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$ C(II,1), LDC, WORK, INFO )
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*
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END IF
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*
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ELSE IF(RIGHT.AND.NOTRAN) THEN
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*
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* Multiply Q to the last block of C
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*
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KK = MOD((N-K),(NB-K))
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CTR = (N-K)/(NB-K)
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IF (KK.GT.0) THEN
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II=N-KK+1
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CALL STPMLQT('R','N',M , KK, K, 0, MB, A(1, II), LDA,
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$ T(1,CTR*K+1), LDT, C(1,1), LDC,
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$ C(1,II), LDC, WORK, INFO )
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ELSE
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II=N+1
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END IF
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*
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DO I=II-(NB-K),NB+1,-(NB-K)
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*
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* Multiply Q to the current block of C (1:M,I:I+MB)
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*
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CTR = CTR - 1
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CALL STPMLQT('R','N', M, NB-K, K, 0, MB, A(1, I), LDA,
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$ T(1,CTR*K+1), LDT, C(1,1), LDC,
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$ C(1,I), LDC, WORK, INFO )
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END DO
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*
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* Multiply Q to the first block of C (1:M,1:MB)
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*
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CALL SGEMLQT('R','N',M , NB, K, MB, A(1,1), LDA, T
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$ ,LDT ,C(1,1), LDC, WORK, INFO )
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*
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ELSE IF (RIGHT.AND.TRAN) THEN
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*
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* Multiply Q to the first block of C
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*
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KK = MOD((N-K),(NB-K))
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II=N-KK+1
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CTR = 1
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CALL SGEMLQT('R','T',M , NB, K, MB, A(1,1), LDA, T
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$ ,LDT ,C(1,1), LDC, WORK, INFO )
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*
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DO I=NB+1,II-NB+K,(NB-K)
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*
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* Multiply Q to the current block of C (1:M,I:I+MB)
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*
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CALL STPMLQT('R','T',M , NB-K, K, 0,MB, A(1,I), LDA,
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$ T(1, CTR*K+1), LDT, C(1,1), LDC,
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$ C(1,I), LDC, WORK, INFO )
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CTR = CTR + 1
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*
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END DO
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IF(II.LE.N) THEN
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*
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* Multiply Q to the last block of C
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*
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CALL STPMLQT('R','T',M , KK, K, 0,MB, A(1,II), LDA,
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$ T(1,CTR*K+1),LDT, C(1,1), LDC,
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$ C(1,II), LDC, WORK, INFO )
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*
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END IF
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*
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END IF
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*
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WORK(1) = LW
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RETURN
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*
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* End of SLAMSWLQ
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*
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END
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