39 lines
1.2 KiB
C++
39 lines
1.2 KiB
C++
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#include <Eigen/Sparse>
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#include <vector>
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#include <iostream>
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typedef Eigen::SparseMatrix<double> SpMat; // declares a column-major sparse matrix type of double
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typedef Eigen::Triplet<double> T;
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void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n);
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void saveAsBitmap(const Eigen::VectorXd& x, int n, const char* filename);
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int main(int argc, char** argv)
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{
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if(argc!=2) {
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std::cerr << "Error: expected one and only one argument.\n";
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return -1;
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}
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int n = 300; // size of the image
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int m = n*n; // number of unknowns (=number of pixels)
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// Assembly:
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std::vector<T> coefficients; // list of non-zeros coefficients
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Eigen::VectorXd b(m); // the right hand side-vector resulting from the constraints
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buildProblem(coefficients, b, n);
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SpMat A(m,m);
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A.setFromTriplets(coefficients.begin(), coefficients.end());
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// Solving:
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Eigen::SimplicialCholesky<SpMat> chol(A); // performs a Cholesky factorization of A
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Eigen::VectorXd x = chol.solve(b); // use the factorization to solve for the given right hand side
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// Export the result to a file:
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saveAsBitmap(x, n, argv[1]);
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return 0;
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}
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