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
main(int argc,char ** argv)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
39