39 lines
1.2 KiB
C++
39 lines
1.2 KiB
C++
#include <Eigen/Sparse>
|
|
#include <vector>
|
|
#include <iostream>
|
|
|
|
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)
|
|
{
|
|
if(argc!=2) {
|
|
std::cerr << "Error: expected one and only one argument.\n";
|
|
return -1;
|
|
}
|
|
|
|
int n = 300; // size of the image
|
|
int m = n*n; // number of unknowns (=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;
|
|
}
|
|
|