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19 lines
752 B
C++
19 lines
752 B
C++
typedef Matrix<double, 5, 3> Matrix5x3;
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typedef Matrix<double, 5, 5> Matrix5x5;
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Matrix5x3 m = Matrix5x3::Random();
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cout << "Here is the matrix m:" << endl << m << endl;
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Eigen::LU<Matrix5x3> lu(m);
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cout << "Here is, up to permutations, its LU decomposition matrix:"
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<< endl << lu.matrixLU() << endl;
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cout << "Here is the actual L matrix in this decomposition:" << endl;
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Matrix5x5 l = Matrix5x5::Identity();
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l.block<5,3>(0,0).part<StrictlyLower>() = lu.matrixLU();
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cout << l << endl;
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cout << "Let us now reconstruct the original matrix m:" << endl;
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Matrix5x3 x = l * lu.matrixU();
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Matrix5x3 y;
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for(int i = 0; i < 5; i++) for(int j = 0; j < 3; j++)
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y(i, lu.permutationQ()[j]) = x(lu.permutationP()[i], j);
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cout << y << endl;
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assert(y.isApprox(m));
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