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test(diffusion): Verify symmetry in diffusion simulation

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Max Lübke 2025-02-06 14:55:54 +01:00
parent 1ca81b4406
commit d8c8a734aa
1 changed files with 44 additions and 0 deletions
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test/testDiffusion.cpp
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@ -214,3 +214,47 @@ DIFFUSION_TEST(ConstantInnerCell) {
EXPECT_FALSE((concentrations_result.array() < 0.0).any());
}
DIFFUSION_TEST(Symmetry) {
// Arrange
constexpr std::size_t rows = 25;
constexpr std::size_t cols = 25;
constexpr std::size_t center_row = rows / 2;
constexpr std::size_t center_col = cols / 2;
tug::RowMajMat<double> concentrations =
tug::RowMajMat<double>::Constant(rows, cols, 1);
tug::RowMajMat<double> alpha =
tug::RowMajMat<double>::Constant(rows, cols, 1E-2);
tug::Diffusion<double, tug::FTCS_APPROACH> sim(concentrations);
sim.setDomain(100, 100);
sim.setAlphaX(alpha);
sim.setAlphaY(alpha);
// choose a high number of iterations, which lead to small changes in ULP
// between symmetric cells
sim.setIterations(10000);
sim.setTimestep(10);
tug::Boundary<double> &bcH = sim.getBoundaryConditions();
bcH.setInnerBoundary(center_row, center_col, 10);
sim.run();
// check symmetry
for (std::size_t i_rows = 0; i_rows <= center_row; i_rows++) {
for (std::size_t i_cols = 0; i_cols <= center_col; i_cols++) {
if (i_rows == center_row && i_cols == center_col) {
continue;
}
// to avoid floating point errors, we check with ASSERT_DOUBLE_EQ with a
// precision of ULP(4), see https://stackoverflow.com/a/4149599
ASSERT_DOUBLE_EQ(concentrations(i_rows, i_cols),
concentrations(rows - i_rows - 1, cols - i_cols - 1));
}
}
}