Tutorial_sparse_example.cpp (1184B)
1 #include <Eigen/Sparse> 2 #include <vector> 3 #include <iostream> 4 5 typedef Eigen::SparseMatrix<double> SpMat; // declares a column-major sparse matrix type of double 6 typedef Eigen::Triplet<double> T; 7 8 void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n); 9 void saveAsBitmap(const Eigen::VectorXd& x, int n, const char* filename); 10 11 int main(int argc, char** argv) 12 { 13 if(argc!=2) { 14 std::cerr << "Error: expected one and only one argument.\n"; 15 return -1; 16 } 17 18 int n = 300; // size of the image 19 int m = n*n; // number of unknowns (=number of pixels) 20 21 // Assembly: 22 std::vector<T> coefficients; // list of non-zeros coefficients 23 Eigen::VectorXd b(m); // the right hand side-vector resulting from the constraints 24 buildProblem(coefficients, b, n); 25 26 SpMat A(m,m); 27 A.setFromTriplets(coefficients.begin(), coefficients.end()); 28 29 // Solving: 30 Eigen::SimplicialCholesky<SpMat> chol(A); // performs a Cholesky factorization of A 31 Eigen::VectorXd x = chol.solve(b); // use the factorization to solve for the given right hand side 32 33 // Export the result to a file: 34 saveAsBitmap(x, n, argv[1]); 35 36 return 0; 37 } 38