1 /*
  2  *   Copyright (c) 2012, 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 DGELQ2( M, N, A, LDA, TAU, WORK, INFO )
 36  *
 37  *  -- LAPACK routine (version 3.3.1) --
 38  *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
 39  *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
 40  *  -- April 2011                                                      --
 41  */
 42 
 43 #ifndef FLENS_LAPACK_LQ_LQ2_TCC
 44 #define FLENS_LAPACK_LQ_LQ2_TCC 1
 45 
 46 #include <flens/blas/blas.h>
 47 #include <flens/lapack/lapack.h>
 48 
 49 namespace flens { namespace lapack {
 50 
 51 //== generic lapack implementation =============================================
 52 
 53 template <typename MA, typename VTAU, typename VWORK>
 54 void
 55 lq2_generic(GeMatrix<MA> &A, DenseVector<VTAU> &tau, DenseVector<VWORK> &work)
 56 {
 57     typedef typename GeMatrix<MA>::ElementType  ElementType;
 58     typedef typename GeMatrix<MA>::IndexType    IndexType;
 59 
 60     const Underscore<IndexType> _;
 61 
 62     const IndexType m = A.numRows();
 63     const IndexType n = A.numCols();
 64     const IndexType k = std::min(m, n);
 65 
 66     const ElementType One(1);
 67 
 68     for (IndexType i=1; i<=k; ++i) {
 69 //
 70 //      Generate elementary reflector H(i) to annihilate A(i,i+1:n)
 71 //
 72         larfg(n-i+1, A(i,i), A(i,_(std::min(i+1,n),n)), tau(i));
 73 
 74         if (i<m) {
 75 //
 76 //          Apply H(i) to A(i+1:m,i:n) from the right
 77 //
 78             const ElementType Aii = A(i,i);
 79             A(i,i) = One;
 80             auto _work = work(_(1, m-i));
 81             larf(Right, A(i,_(i,n)), tau(i), A(_(i+1,m), _(i,n)), _work);
 82             A(i,i) = Aii;
 83         }
 84     }
 85 }
 86 
 87 //== interface for native lapack ===============================================
 88 
 89 #ifdef CHECK_CXXLAPACK
 90 
 91 template <typename MA, typename VTAU, typename VWORK>
 92 void
 93 lq2_native(GeMatrix<MA> &A, DenseVector<VTAU> &tau, DenseVector<VWORK> &work)
 94 {
 95     typedef typename GeMatrix<MA>::ElementType  T;
 96 
 97     const INTEGER    M = A.numRows();
 98     const INTEGER    N = A.numCols();
 99     const INTEGER    LDA = A.leadingDimension();
100     INTEGER          INFO;
101 
102     if (IsSame<T, DOUBLE>::value) {
103         LAPACK_IMPL(dgelq2)(&M, &N, A.data(), &LDA,
104                             tau.data(), work.data(),
105                             &INFO);
106         assert(INFO==0);
107     } else {
108         ASSERT(0);
109     }
110 }
111 
112 #endif // CHECK_CXXLAPACK
113 
114 //== public interface ==========================================================
115 
116 template <typename MA, typename VTAU, typename VWORK>
117 void
118 lq2(GeMatrix<MA> &A, DenseVector<VTAU> &tau, DenseVector<VWORK> &work)
119 {
120     typedef typename GeMatrix<MA>::IndexType  IndexType;
121 
122 //
123 //  Test the input parameters
124 //
125 #   ifndef NDEBUG
126     ASSERT(A.firstRow()==1);
127     ASSERT(A.firstCol()==1);
128     ASSERT(tau.firstIndex()==1);
129     ASSERT(work.firstIndex()==1);
130 
131     const IndexType m = A.numRows();
132     const IndexType n = A.numCols();
133     const IndexType k = std::min(m, n);
134 
135     ASSERT(tau.length()>=k);
136     ASSERT(work.length()>=m);
137 #   endif
138 
139 #   ifdef CHECK_CXXLAPACK
140 //
141 //  Make copies of output arguments
142 //
143     typename GeMatrix<MA>::NoView       A_org      = A;
144     typename DenseVector<VTAU>::NoView  tau_org    = tau;
145     typename DenseVector<VTAU>::NoView  work_org   = work;
146 #   endif
147 
148 //
149 //  Call implementation
150 //
151     lq2_generic(A, tau, work);
152 
153 #   ifdef CHECK_CXXLAPACK
154 //
155 //  Restore output arguments
156 //
157     typename GeMatrix<MA>::NoView       A_generic      = A;
158     typename DenseVector<VTAU>::NoView  tau_generic    = tau;
159     typename DenseVector<VTAU>::NoView  work_generic   = work;
160 
161     A = A_org;
162     tau = tau_org;
163     work = work_org;
164 //
165 //  Compare results
166 //
167     lq2_native(A, tau, work);
168 
169     bool failed = false;
170     if (! isIdentical(A_generic, A, "A_generic""A")) {
171         std::cerr << "CXXLAPACK: A_generic = " << A_generic << std::endl;
172         std::cerr << "F77LAPACK: A = " << A << std::endl;
173         failed = true;
174     }
175 
176     if (! isIdentical(tau_generic, tau, "tau_generic""tau")) {
177         std::cerr << "CXXLAPACK: tau_generic = " << tau_generic << std::endl;
178         std::cerr << "F77LAPACK: tau = " << tau << std::endl;
179         failed = true;
180     }
181 
182     if (! isIdentical(work_generic, work, "work_generic""work")) {
183         std::cerr << "CXXLAPACK: work_generic = " << work_generic << std::endl;
184         std::cerr << "F77LAPACK: work = " << work << std::endl;
185         failed = true;
186     }
187 
188     if (failed) {
189         ASSERT(0);
190     }
191 #   endif
192 }
193 
194 //-- forwarding ----------------------------------------------------------------
195 template <typename MA, typename VTAU, typename VWORK>
196 void
197 lq2(MA &&A, VTAU &&tau, VWORK &&work)
198 {
199     CHECKPOINT_ENTER;
200     lq2(A, tau, work);
201     CHECKPOINT_LEAVE;
202 }
203 
204 } } // namespace lapack, flens
205 
206 #endif // FLENS_LAPACK_LQ_LQ2_TCC