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https://github.com/triqs/dft_tools
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b534936589
- The previous version of the * operator for matrix was too clever. It was giving a lazy object and then rewriting C = A *B into gemm (a,A,B,0,C). The pb was in case of aliasing : when e.g. C = A, or is a part of A. gemm is not correct that case, and as a result generic code like a = a *b may not be correct in matrix case, which is unacceptable. - So we revert to a simple * operator for matrix that does immediate computation. Same thing for matrix* vector - we also suppress a_x_ty class. -> for M = a * b, when M is a matrix, there is no overhead due to move assignment -> however, when M is a view, there is an additionnal copy. -Correctness comes first, hence the fix. However, if one wants more speed and one can guarantee that there is no aliasing possible, then one has to write a direct gemm call. -> det_manip class was adapted, since in that case, we can show there no alias, and we want the speed gain, so the * ops where replaced by direct blas call (using the array blas interface). -> also gemm, gemv, ger were overloaded in the case the return matrix/vector (i.e. last parameter of the function) is not an lvalue, but a temporary view created on the fly.
64 lines
1.6 KiB
C++
64 lines
1.6 KiB
C++
/*******************************************************************************
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*
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* TRIQS: a Toolbox for Research in Interacting Quantum Systems
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*
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* Copyright (C) 2011 by O. Parcollet
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*
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* TRIQS is free software: you can redistribute it and/or modify it under the
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* terms of the GNU General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* TRIQS. If not, see <http://www.gnu.org/licenses/>.
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*
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******************************************************************************/
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#include <triqs/arrays.hpp>
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using namespace std;
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using namespace triqs;
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using namespace triqs::arrays;
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struct gemv_via_binder {
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triqs::arrays::matrix<double> A;
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typedef triqs::arrays::vector<double> vector_type;
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vector_type MC, MB;
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static const unsigned int N =200;
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gemv_via_binder(): A(N,N,FORTRAN_LAYOUT), MC(N), MB(N) {
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for (int i =0; i<N; ++i)
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for (int j=0; j<N; ++j)
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A(i,j) = 0.1*(10*i+ j);
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make_view(MC) = 1;
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}
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void operator()() {
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blas::gemv(1,A, MC, 0, MB);
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}
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};
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struct expressif : gemv_via_binder {
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void operator()() {
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MB = A * MC;
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}
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};
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#include "./speed_tester.hpp"
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int main() {
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const int l= 1000*1000;
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speed_tester<gemv_via_binder> (l);
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speed_tester<expressif> (l);
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return 0;
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}
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