#include <Eigen/Sparse> #include <vector> typedef Eigen::SparseMatrix<double> SpMat; // declares a column-major sparse matrix type of double typedef Eigen::Triplet<double> T; void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n); void saveAsBitmap(const Eigen::VectorXd& x, int n, const char* filename); int main(int argc, char** argv) { int n = 300; // size of the image int m = n*n; // number of unknows (=number of pixels) // Assembly: std::vector<T> coefficients; // list of non-zeros coefficients Eigen::VectorXd b(m); // the right hand side-vector resulting from the constraints buildProblem(coefficients, b, n); SpMat A(m,m); A.setFromTriplets(coefficients.begin(), coefficients.end()); // Solving: Eigen::SimplicialCholesky<SpMat> chol(A); // performs a Cholesky factorization of A Eigen::VectorXd x = chol.solve(b); // use the factorization to solve for the given right hand side // Export the result to a file: saveAsBitmap(x, n, argv[1]); return 0; }