67 lines
2.4 KiB
C++
67 lines
2.4 KiB
C++
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#include <Eigen/Core>
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#include <iostream>
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using namespace Eigen;
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// [functor]
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template<class ArgType, class RowIndexType, class ColIndexType>
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class indexing_functor {
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const ArgType &m_arg;
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const RowIndexType &m_rowIndices;
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const ColIndexType &m_colIndices;
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public:
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typedef Matrix<typename ArgType::Scalar,
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RowIndexType::SizeAtCompileTime,
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ColIndexType::SizeAtCompileTime,
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ArgType::Flags&RowMajorBit?RowMajor:ColMajor,
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RowIndexType::MaxSizeAtCompileTime,
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ColIndexType::MaxSizeAtCompileTime> MatrixType;
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indexing_functor(const ArgType& arg, const RowIndexType& row_indices, const ColIndexType& col_indices)
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: m_arg(arg), m_rowIndices(row_indices), m_colIndices(col_indices)
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{}
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const typename ArgType::Scalar& operator() (Index row, Index col) const {
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return m_arg(m_rowIndices[row], m_colIndices[col]);
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}
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};
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// [functor]
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// [function]
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template <class ArgType, class RowIndexType, class ColIndexType>
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CwiseNullaryOp<indexing_functor<ArgType,RowIndexType,ColIndexType>, typename indexing_functor<ArgType,RowIndexType,ColIndexType>::MatrixType>
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mat_indexing(const Eigen::MatrixBase<ArgType>& arg, const RowIndexType& row_indices, const ColIndexType& col_indices)
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{
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typedef indexing_functor<ArgType,RowIndexType,ColIndexType> Func;
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typedef typename Func::MatrixType MatrixType;
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return MatrixType::NullaryExpr(row_indices.size(), col_indices.size(), Func(arg.derived(), row_indices, col_indices));
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}
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// [function]
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int main()
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{
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std::cout << "[main1]\n";
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Eigen::MatrixXi A = Eigen::MatrixXi::Random(4,4);
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Array3i ri(1,2,1);
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ArrayXi ci(6); ci << 3,2,1,0,0,2;
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Eigen::MatrixXi B = mat_indexing(A, ri, ci);
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std::cout << "A =" << std::endl;
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std::cout << A << std::endl << std::endl;
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std::cout << "A([" << ri.transpose() << "], [" << ci.transpose() << "]) =" << std::endl;
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std::cout << B << std::endl;
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std::cout << "[main1]\n";
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std::cout << "[main2]\n";
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B = mat_indexing(A, ri+1, ci);
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std::cout << "A(ri+1,ci) =" << std::endl;
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std::cout << B << std::endl << std::endl;
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#if EIGEN_COMP_CXXVER >= 11
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B = mat_indexing(A, ArrayXi::LinSpaced(13,0,12).unaryExpr([](int x){return x%4;}), ArrayXi::LinSpaced(4,0,3));
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std::cout << "A(ArrayXi::LinSpaced(13,0,12).unaryExpr([](int x){return x%4;}), ArrayXi::LinSpaced(4,0,3)) =" << std::endl;
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std::cout << B << std::endl << std::endl;
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#endif
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std::cout << "[main2]\n";
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}
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