问使用特征3/稀疏的稀疏特征值

EN

#include <Eigen/Core>
#include <SymEigsSolver.h>  // Also includes <MatOp/DenseSymMatProd.h>
#include <iostream>
#include <limits>

int main()
{
    using Real=long double;
    using Matrix=Eigen::Matrix<Real, Eigen::Dynamic, Eigen::Dynamic>;

    // We are going to calculate the eigenvalues of M
    const auto A = Matrix::Random(10, 10);
    const Matrix M = A + A.transpose();

    // Construct matrix operation object using the wrapper class DenseGenMatProd
    Spectra::DenseSymMatProd<Real> op(M);

    // Construct eigen solver object, requesting the largest three eigenvalues
    Spectra::SymEigsSolver<Real,
                           Spectra::LARGEST_ALGE,
                           Spectra::DenseSymMatProd<Real>> eigs(&op, 3, 6);

    // Initialize and compute
    eigs.init();
    const auto nconv = eigs.compute();
    std::cout << nconv << " eigenvalues converged.\n";

    // Retrieve results
    if(eigs.info() == Spectra::SUCCESSFUL)
    {
        const auto evalues = eigs.eigenvalues();
        std::cout.precision(std::numeric_limits<Real>::digits10);
        std::cout << "Eigenvalues found:\n" << evalues << '\n';
    }
}