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eigen/doc/examples/function_taking_ref.cpp
2026-05-04 00:36:12 +00:00

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C++

// SPDX-FileCopyrightText: The Eigen Authors
// SPDX-License-Identifier: MPL-2.0
#include <iostream>
#include <Eigen/SVD>
float inv_cond(const Eigen::Ref<const Eigen::MatrixXf>& a) {
const Eigen::VectorXf sing_vals = a.jacobiSvd().singularValues();
return sing_vals(sing_vals.size() - 1) / sing_vals(0);
}
int main() {
Eigen::MatrixXf m = Eigen::MatrixXf::Random(4, 4);
std::cout << "matrix m:\n" << m << "\n\n";
std::cout << "inv_cond(m): " << inv_cond(m) << "\n";
std::cout << "inv_cond(m(1:3,1:3)): " << inv_cond(m.topLeftCorner(3, 3)) << "\n";
std::cout << "inv_cond(m+I): " << inv_cond(m + Eigen::MatrixXf::Identity(4, 4)) << "\n";
}