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implement 1D

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This commit is contained in:
Max Lübke 2021-11-11 11:53:14 +01:00
parent 8dff22c7bf
commit d188575105
1 changed files with 61 additions and 2 deletions
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63
src/diffusion.cpp
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@ -13,8 +13,67 @@
#include <Eigen/src/SparseLU/SparseLU.h>
#include <Eigen/src/SparseQR/SparseQR.h>
#include <iostream>
#include <iomanip>
#include <ostream>
void BTCS1D(int x, std::vector<double> &c, std::vector<double> &alpha,
double timestep, std::vector<double> &bc) {
double dx = 1. / x;
int size = x + 2;
Eigen::VectorXd b = Eigen::VectorXd::Constant(size, 0);
Eigen::VectorXd x_out(size);
std::vector<T> tripletList;
tripletList.reserve(c.size() * 3 + bc.size());
int A_line = 0;
for (int i = 1; i < x + 1; i++) {
double sx = (alpha[i-1] * timestep) / (dx * dx);
tripletList.push_back(T(A_line, i, (-1. - 2. * sx)));
tripletList.push_back(T(A_line, i - 1, sx));
tripletList.push_back(T(A_line, i + 1, sx));
b[A_line] = -c[i-1];
A_line++;
}
tripletList.push_back(T(A_line, 0, 1));
b[A_line] = bc[0];
A_line++;
tripletList.push_back(T(A_line, size-1, 1));
b[A_line] = bc[1];
// std::cout << b << std::endl;
Eigen::SparseMatrix<double> A(size, size);
A.setFromTriplets(tripletList.begin(), tripletList.end());
// std::cout << A << std::endl;
Eigen::SparseQR<Eigen::SparseMatrix<double>, Eigen::COLAMDOrdering<int>>
solver;
// Eigen::SparseLU<Eigen::SparseMatrix<double>, Eigen::COLAMDOrdering<int>>
// solver;
solver.analyzePattern(A);
solver.factorize(A);
std::cout << solver.lastErrorMessage() << std::endl;
x_out = solver.solve(b);
std::cout << std::setprecision(10) << x_out << std::endl << std::endl;
for (int i=0; i < c.size(); i++) {
c[i] = x_out[i+1];
}
}
void BTCS2D(int x, int y, std::vector<double> &c, std::vector<double> &alpha,
double timestep) {
@ -44,14 +103,14 @@ void BTCS2D(int x, int y, std::vector<double> &c, std::vector<double> &alpha,
tripletList.push_back(T(A_line, i * x + (j + 1), sx));
tripletList.push_back(T(A_line, i * x + (j - 1), sx));
b[A_line] = -c[i*x+j];
b[A_line] = -c[i * x + j];
A_line++;
}
}
std::cout << b << std::endl;
Eigen::SparseMatrix<double> A(size, x*y);
Eigen::SparseMatrix<double> A(size, x * y);
A.setFromTriplets(tripletList.begin(), tripletList.end());
Eigen::SparseQR<Eigen::SparseMatrix<double>, Eigen::COLAMDOrdering<int>>