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54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
#include "diffusion.hpp"
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#include <Eigen/SparseLU>
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#include <Eigen/src/Core/Matrix.h>
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#include <Eigen/src/Core/util/Constants.h>
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#include <Eigen/src/OrderingMethods/Ordering.h>
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#include <Eigen/src/SparseCore/SparseMap.h>
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#include <Eigen/src/SparseCore/SparseMatrix.h>
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#include <Eigen/src/SparseCore/SparseMatrixBase.h>
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#include <Eigen/src/SparseLU/SparseLU.h>
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#include <iostream>
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void BTCS2D(int x, int y, std::vector<double> &c, std::vector<double> &alpha,
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double timestep) {
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double dx = 1. / x;
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double dy = 1. / y;
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int size = x * y;
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Eigen::VectorXd b = Eigen::VectorXd::Constant(size, 0);
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Eigen::VectorXd x_out(size);
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std::vector<T> tripletList;
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tripletList.reserve(((x - 1) * (y - 1) * 5));
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for (int i = 1; i < y - 1; i++) {
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for (int j = 1; j < x - 1; j++) {
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double sx = (alpha[i * y + j] * timestep) / (dx * dx);
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double sy = (alpha[i * y + j] * timestep) / (dy * dy);
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tripletList.push_back(T((i * x) + j, (i * x) + j, (1 + 2 * sx + 2 * sy)));
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tripletList.push_back(T((i * x) + j, ((i * x) + j) + x, sy));
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tripletList.push_back(T((i * x) + j, ((i * x) + j) - x, sy));
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tripletList.push_back(T((i * x) + j, ((i * x) + j) + 1, sx));
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tripletList.push_back(T((i * x) + j, ((i * x) + j) - 1, sx));
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b[(i * x) + j] = -c[(i * x) + j];
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}
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}
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Eigen::SparseMatrix<double> A(size, size);
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A.setFromTriplets(tripletList.begin(), tripletList.end());
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Eigen::SparseLU<Eigen::SparseMatrix<double>, Eigen::COLAMDOrdering<int>>
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solver;
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solver.analyzePattern(A);
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solver.factorize(A);
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std::cout << A << std::endl;
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x_out = solver.solve(b);
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}
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