2013-07-17 19:24:07 +02:00
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/*******************************************************************************
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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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#ifndef TRIQS_LINALG_CROSS_PRODUCT_H
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#define TRIQS_LINALG_CROSS_PRODUCT_H
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#include <triqs/utility/exceptions.hpp>
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namespace triqs { namespace arrays {
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/** Cross product. Dim 3 only */
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template<typename VectorType>
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Fix matrix * alias issue and adapt det_manip
- 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.
2013-09-10 21:41:17 +02:00
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vector<typename std::remove_const<typename VectorType::value_type >::type>
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cross_product (VectorType const & A, VectorType const & B) {
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2013-07-17 19:24:07 +02:00
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if (A.shape()[0] !=3) TRIQS_RUNTIME_ERROR<<"arrays::linalg::cross_product : works only in d=3 while you gave a vector of size "<<A.shape()[0];
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if (B.shape()[0] !=3) TRIQS_RUNTIME_ERROR<<"arrays::linalg::cross_product : works only in d=3 while you gave a vector of size "<<B.shape()[0];
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Fix matrix * alias issue and adapt det_manip
- 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.
2013-09-10 21:41:17 +02:00
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vector<typename std::remove_const<typename VectorType::value_type >::type > r(3);
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2013-07-17 19:24:07 +02:00
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r(0) = A(1)* B(2) - B(1) * A(2);
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r(1) = - A(0)* B(2) + B(0) * A(2);
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r(2) = A(0)*B(1) - B(0) * A(1);
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return r;
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}
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}}//namespace triqs::arrays
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#endif
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