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WIP: locator review

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Vasco C. B. Ferreira
2026-08-01 19:02:22 +02:00
parent 4b48ea3037
commit 7d05f2f22a
2 changed files with 7 additions and 22 deletions
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nufi/cells.h
+5 -21
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@@ -33,9 +33,7 @@ private:
// Cached base level = Parameters::GLOBAL_REFINEMENT.
unsigned int base_level = 0;
unsigned int base_n_per_axis = 1; // 2^base_level
// Flat lookup, indexed in the same bit-interleaved order that
// GeometryInfo<dim>::child_cell_from_point produces at each level,
// so base_cells[idx] can be found with pure bit math, no tree walk.
std::vector<typename Triangulation<dim>::cell_iterator> base_cells;
};
@@ -52,16 +50,12 @@ void CellLocator<dim>::rebuild(const DoFHandler<dim> &dof_handler,
upper = root->vertex(GeometryInfo<dim>::vertices_per_cell - 1);
base_level = Parameters::GLOBAL_REFINEMENT;
base_n_per_axis = 1u << base_level;
base_n_per_axis = 1u << base_level; // = 2^base_level
// Walk down exactly base_level times ONCE per base cell to build the
// flat table. This costs O(2^(dim*base_level)) total at rebuild time
// (proportional to the number of base cells), not per locate() call.
const unsigned int n_base_cells = 1u << (dim * base_level);
const unsigned int n_base_cells =
1u << (dim * base_level); // = 2^(dim*base_level)
base_cells.assign(n_base_cells, typename Triangulation<dim>::cell_iterator());
// Recursive-free BFS/DFS: descend from root, tracking the accumulated
// child-index bits per level to know where to store each level-G cell.
std::vector<typename Triangulation<dim>::cell_iterator> stack;
std::vector<unsigned int> index_stack;
std::vector<unsigned int> depth_stack;
@@ -82,8 +76,6 @@ void CellLocator<dim>::rebuild(const DoFHandler<dim> &dof_handler,
continue;
}
// At this point cell must have children, since refine_global(base_level)
// guarantees a fully uniform tree down to base_level.
AssertThrow(cell->has_children(),
ExcMessage("CellLocator: mesh is not uniformly refined to "
"Parameters::GLOBAL_REFINEMENT; base-level cache "
@@ -104,7 +96,6 @@ CellLocation<dim> CellLocator<dim>::locate(const Point<dim> &p) const {
AssertThrow(dof_handler_ptr != nullptr,
ExcMessage("CellLocator::rebuild() has not been called."));
// Step 1: periodic wrap into [lower, upper) per axis.
Point<dim> p_wrapped;
for (unsigned int d = 0; d < dim; ++d) {
const double L = upper[d] - lower[d];
@@ -113,19 +104,12 @@ CellLocation<dim> CellLocator<dim>::locate(const Point<dim> &p) const {
p_wrapped[d] = lower[d] + x;
}
// Step 2: reference coordinates in the root cell, clamped against
// floating-point drift at the domain boundary.
Point<dim> xi;
for (unsigned int d = 0; d < dim; ++d) {
xi[d] = (p_wrapped[d] - lower[d]) / (upper[d] - lower[d]);
xi[d] = std::min(std::max(xi[d], 0.0), 1.0);
xi[d] = std::min(std::max(xi[d], 0.0), 1.0); // of cell at base level
}
// Step 3: O(1) jump to the base-level (GLOBAL_REFINEMENT) cell via index
// math, replacing what used to be `base_level` iterations of the
// has_children() loop. Must mirror the same bit convention used when
// building base_cells in rebuild() (child index accumulated as
// idx = idx*n_children + child_cell_from_point(xi) at each level).
unsigned int idx = 0;
Point<dim> xi_local = xi;
for (unsigned int l = 0; l < base_level; ++l) {