Tutorial_sparse_example_details.cpp File Reference

#include <Eigen/Sparse>
#include <vector>
#include <QImage>

Typedefs
typedef Eigen::SparseMatrix< double >	SpMat
typedef Eigen::Triplet< double >	T

Functions
void	insertCoefficient (int id, int i, int j, double w, std::vector< T > &coeffs, Eigen::VectorXd &b, const Eigen::VectorXd &boundary)
void	buildProblem (std::vector< T > &coefficients, Eigen::VectorXd &b, int n)
void	saveAsBitmap (const Eigen::VectorXd &x, int n, const char *filename)

Typedef Documentation

SpMat

typedef Eigen::SparseMatrix<double> SpMat

T

typedef Eigen::Triplet<double> T

Function Documentation

buildProblem()

void buildProblem	(	std::vector< T > &	coefficients,
		Eigen::VectorXd &	b,
		int	n
	)

                                                                       {
  b.setZero();
  Eigen::ArrayXd boundary = Eigen::ArrayXd::LinSpaced(n, 0, M_PI).sin().pow(2);
  for (int j = 0; j < n; ++j) {
    for (int i = 0; i < n; ++i) {
      int id = i + j * n;
      insertCoefficient(id, i - 1, j, -1, coefficients, b, boundary);
      insertCoefficient(id, i + 1, j, -1, coefficients, b, boundary);
      insertCoefficient(id, i, j - 1, -1, coefficients, b, boundary);
      insertCoefficient(id, i, j + 1, -1, coefficients, b, boundary);
      insertCoefficient(id, i, j, 4, coefficients, b, boundary);
    }
  }
}

References b, i, insertCoefficient(), j, M_PI, and n.

Referenced by main().

insertCoefficient()

void insertCoefficient	(	int	id,
		int	i,
		int	j,
		double	w,
		std::vector< T > &	coeffs,
		Eigen::VectorXd &	b,
		const Eigen::VectorXd &	boundary
	)

                                                      {
  int n = int(boundary.size());
  int id1 = i + j * n;
 
  if (i == -1 || i == n)
    b(id) -= w * boundary(j);  // constrained coefficient
  else if (j == -1 || j == n)
    b(id) -= w * boundary(i);  // constrained coefficient
  else
    coeffs.push_back(T(id, id1, w));  // unknown coefficient
}

References b, i, int(), j, n, and w.

Referenced by buildProblem().

saveAsBitmap()

void saveAsBitmap	(	const Eigen::VectorXd &	x,
		int	n,
		const char *	filename
	)

                                                                       {
  Eigen::Array<unsigned char, Eigen::Dynamic, Eigen::Dynamic> bits = (x * 255).cast<unsigned char>();
  QImage img(bits.data(), n, n, QImage::Format_Indexed8);
  img.setColorCount(256);
  for (int i = 0; i < 256; i++) img.setColor(i, qRgb(i, i, i));
  img.save(filename);
}

References Eigen::test::bits(), MergeRestartFiles::filename, i, n, and plotDoE::x.

Referenced by main().