1 /*
 2  *   Copyright (c) 2011, Michael Lehn
 3  *
 4  *   All rights reserved.
 5  *
 6  *   Redistribution and use in source and binary forms, with or without
 7  *   modification, are permitted provided that the following conditions
 8  *   are met:
 9  *
10  *   1) Redistributions of source code must retain the above copyright
11  *      notice, this list of conditions and the following disclaimer.
12  *   2) Redistributions in binary form must reproduce the above copyright
13  *      notice, this list of conditions and the following disclaimer in
14  *      the documentation and/or other materials provided with the
15  *      distribution.
16  *   3) Neither the name of the FLENS development group nor the names of
17  *      its contributors may be used to endorse or promote products derived
18  *      from this software without specific prior written permission.
19  *
20  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23  *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24  *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25  *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26  *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 /*  Based on
34  *
35       SUBROUTINE DGEQRS( M, N, NRHS, A, LDA, TAU, B, LDB, WORK, LWORK,
36      $                   INFO )
37  *
38  *  -- LAPACK routine (version 3.0) --
39  *     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
40  *     Courant Institute, Argonne National Lab, and Rice University
41  *     February 29, 1992
42  */
43 
44 #ifndef FLENS_LAPACK_QR_QRS_TCC
45 #define FLENS_LAPACK_QR_QRS_TCC 1
46 
47 #include <flens/blas/blas.h>
48 #include <flens/lapack/lapack.h>
49 
50 namespace flens { namespace lapack {
51 
52 //-- forwarding ----------------------------------------------------------------
53 template <typename MA, typename VTAU, typename MB, typename VWORK>
54 void
55 qrs(MA &&A, const VTAU &tau, MB &&B, VWORK &&work)
56 {
57     qrs(A, tau, B, work);
58 }
59 
60 //-- qrs -----------------------------------------------------------------------
61 template <typename MA, typename VTAU, typename MB, typename VWORK>
62 void
63 qrs(GeMatrix<MA> &A, const DenseVector<VTAU> &tau, GeMatrix<MB> &B,
64     DenseVector<VWORK> &work)
65 {
66     ASSERT(work.length()>=B.numCols());
67 
68     typedef typename GeMatrix<MA>::IndexType    IndexType;
69     typedef typename GeMatrix<MA>::ElementType  T;
70 
71     const Underscore<IndexType> _;
72 
73     const IndexType m = A.numRows();
74     const IndexType n = A.numCols();
75     const IndexType nRhs = B.numCols();
76 
77 //
78 //  Quick return if possible
79 //
80     if ((n==0) || (nRhs==0) || (m==0)) {
81         return;
82     }
83 //
84 //  B := Q' * B
85 //
86     ormqr(Left, Trans, A, tau, B, work);
87 //
88 //  Solve R*X = B(1:n,:)
89 //
90     blas::sm(Left, NoTrans, T(1), A.upper(), B);
91 }
92 
93 } } // namespace lapack, flens
94 
95 #endif // FLENS_LAPACK_QR_QRS_TCC