61 lines
2.5 KiB
C++
61 lines
2.5 KiB
C++
#include <Eigen/Core>
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#include <iostream>
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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 Eigen::Matrix<typename ArgType::Scalar, RowIndexType::SizeAtCompileTime, ColIndexType::SizeAtCompileTime,
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ArgType::Flags & Eigen::RowMajorBit ? Eigen::RowMajor : Eigen::ColMajor,
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RowIndexType::MaxSizeAtCompileTime, ColIndexType::MaxSizeAtCompileTime>
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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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const typename ArgType::Scalar& operator()(Eigen::Index row, Eigen::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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Eigen::CwiseNullaryOp<indexing_functor<ArgType, RowIndexType, ColIndexType>,
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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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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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std::cout << "[main1]\n";
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Eigen::MatrixXi A = Eigen::MatrixXi::Random(4, 4);
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Eigen::Array3i ri(1, 2, 1);
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Eigen::ArrayXi ci(6);
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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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B = mat_indexing(A, Eigen::ArrayXi::LinSpaced(13, 0, 12).unaryExpr([](int x) { return x % 4; }),
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Eigen::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)) ="
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<< std::endl;
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std::cout << B << std::endl << std::endl;
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std::cout << "[main2]\n";
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}
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