1 #include <Eigen/Sparse> 2 #include <vector> 3 4 typedef Eigen::SparseMatrix<double> SpMat; // declares a column-major sparse matrix type of double 5 typedef Eigen::Triplet<double> T; 6 7 void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n); 8 void saveAsBitmap(const Eigen::VectorXd& x, int n, const char* filename); 9 10 int main(int argc, char** argv) 11 { 12 assert(argc==2); 13 14 int n = 300; // size of the image 15 int m = n*n; // number of unknows (=number of pixels) 16 17 // Assembly: 18 std::vector<T> coefficients; // list of non-zeros coefficients 19 Eigen::VectorXd b(m); // the right hand side-vector resulting from the constraints 20 buildProblem(coefficients, b, n); 21 22 SpMat A(m,m); 23 A.setFromTriplets(coefficients.begin(), coefficients.end()); 24 25 // Solving: 26 Eigen::SimplicialCholesky<SpMat> chol(A); // performs a Cholesky factorization of A 27 Eigen::VectorXd x = chol.solve(b); // use the factorization to solve for the given right hand side 28 29 // Export the result to a file: 30 saveAsBitmap(x, n, argv[1]); 31 32 return 0; 33 } 34 35
