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Prepare setup of matrix A for new equation

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This commit is contained in:
Max Luebke 2022-04-06 09:50:08 +02:00
parent fedd80aa0c
commit 9faa4e79bb
1 changed files with 12 additions and 5 deletions
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17
src/BTCSDiffusion.cpp
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@ -28,8 +28,6 @@
constexpr int BTCS_MAX_DEP_PER_CELL = 3; constexpr int BTCS_MAX_DEP_PER_CELL = 3;
constexpr int BTCS_2D_DT_SIZE = 2; constexpr int BTCS_2D_DT_SIZE = 2;
constexpr double center_eq(double sx) { return -1. - 2. * sx; }
Diffusion::BTCSDiffusion::BTCSDiffusion(unsigned int dim) : grid_dim(dim) { Diffusion::BTCSDiffusion::BTCSDiffusion(unsigned int dim) : grid_dim(dim) {
grid_cells.resize(dim, 1); grid_cells.resize(dim, 1);
@ -239,16 +237,25 @@ void Diffusion::BTCSDiffusion::fillMatrixFromRow(
if (left_constant) { if (left_constant) {
A_matrix.insert(1, 1) = 1; A_matrix.insert(1, 1) = 1;
} else {
double sx = (alpha[0] * time_step) / (dx * dx);
A_matrix.insert(1, 1) = -1. - 2. * sx;
A_matrix.insert(1, 0) = sx;
A_matrix.insert(1, 2) = sx;
} }
A_matrix.insert(A_size - 1, A_size - 1) = 1; A_matrix.insert(A_size - 1, A_size - 1) = 1;
if (right_constant) { if (right_constant) {
A_matrix.insert(A_size - 2, A_size - 2) = 1; A_matrix.insert(A_size - 2, A_size - 2) = 1;
} else {
double sx = (alpha[size - 1] * time_step) / (dx * dx);
A_matrix.insert(A_size - 2, A_size - 2) = -1. - 2. * sx;
A_matrix.insert(A_size - 2, A_size - 3) = sx;
A_matrix.insert(A_size - 2, A_size - 1) = sx;
} }
for (int j = 1 + (int)left_constant, k = j - 1; for (int j = 2, k = j - 1; k < size - 1; j++, k++) {
k < size - (int)right_constant; j++, k++) {
double sx = (alpha[k] * time_step) / (dx * dx); double sx = (alpha[k] * time_step) / (dx * dx);
if (bc[k].type == Diffusion::BC_CONSTANT) { if (bc[k].type == Diffusion::BC_CONSTANT) {
@ -256,7 +263,7 @@ void Diffusion::BTCSDiffusion::fillMatrixFromRow(
continue; continue;
} }
A_matrix.insert(j, j) = center_eq(sx); A_matrix.insert(j, j) = -1. - 2. * sx;
A_matrix.insert(j, (j - 1)) = sx; A_matrix.insert(j, (j - 1)) = sx;
A_matrix.insert(j, (j + 1)) = sx; A_matrix.insert(j, (j + 1)) = sx;
} }