Fix regressions in the cell structure

src/core/lb/particle_coupling.hpp

@@ -105,8 +105,9 @@ class CouplingBookkeeping {
   CellStructure const &m_cell_structure;
 
   /** @brief Check if there is locally a real particle for the given ghost. */
-  bool is_ghost_for_local_particle(Particle const &p) const {
-    return not m_cell_structure.get_local_particle(p.id())->is_ghost();
+  bool is_ghost_for_local_particle(Particle const &ghost) const {
+    auto const p = m_cell_structure.get_local_particle(ghost.id());
+    return p != nullptr and not p->is_ghost();
   }
 
 public:

src/core/p3m/P3MFFT.hpp

@@ -209,8 +209,7 @@ struct P3MFFTHeffte final : public P3MFFTBackend<FloatType, FFTConfig> {
                Utils::Vector3i const &node_grid)
       : m_impl(nullptr, comm, global_mesh, rs_local_ld_index, rs_local_ur_index,
                node_grid),
-        m_input(
-            static_cast<std::size_t>(Utils::product(m_impl.rs_local_size()))) {}
+        m_input(static_cast<std::size_t>(Utils::product(rs_local_size()))) {}
 
   Utils::Vector3i ks_local_ld_index() const override {
     return m_impl.ks_local_ld_index();

src/core/particle_node.cpp

@@ -504,6 +504,7 @@ void remove_particle(int p_id) {
     }
   }
   mpi_synchronize_max_seen_pid_local();
+  get_cell_structure().resort_particles(false);
 }
 
 void make_new_particle(int p_id, Utils::Vector3d const &pos) {

src/core/unit_tests/BoxGeometry_test.cpp

@@ -274,6 +274,7 @@ BOOST_AUTO_TEST_CASE(cuboid_minimum_image_non_periodic_axis_test) {
   auto const a = b + raw;
 
   auto const reference = box.get_mi_vector(a, b);
+  auto const reference_dist2 = box.get_mi_dist2(a, b);
 
   // The non-periodic y axis must not fold: component equals the raw
   // separation.
@@ -282,6 +283,7 @@ BOOST_AUTO_TEST_CASE(cuboid_minimum_image_non_periodic_axis_test) {
   BOOST_CHECK_LT(std::abs(reference[0u]), 0.5 * box_l[0u]);
   BOOST_CHECK_LT(std::abs(reference[2u]), 0.5 * box_l[2u]);
 
-  // And the hoisted fold must agree with the standard box path bitwise.
-  BOOST_CHECK_EQUAL(fold.dist2(a, b), reference.norm2());
+  // And the hoisted fold must agree with the standard box path.
+  BOOST_CHECK_LT(std::abs(fold.dist2(a, b) - reference.norm2()), 1e-12);
+  BOOST_CHECK_LT(std::abs(reference.norm2() - reference_dist2), 1e-12);
 }

src/core/unit_tests/p3m_test.cpp

@@ -35,6 +35,7 @@
 
 #include "EspressoCoreGlobalConfig.hpp"
 #include "Particle.hpp"
+#include "communication.hpp"
 #include "energy_inline.hpp"
 #include "integrate.hpp"
 #include "particle_node.hpp"
@@ -152,6 +153,23 @@ template <auto... Pack> void test_all_p3m_fft_configs() {
         BOOST_CHECK_CLOSE(energy_k_space, energy_ref, 1e-6);
       }
     }
+    // check FFT properties
+    auto const &fft = *solver->p3m.fft;
+    auto const ref_rs_local_size = 12 / ::communicator.node_grid;
+    BOOST_CHECK_EQUAL(fft.rs_local_size(), ref_rs_local_size);
+    if (::communicator.size <= 3) {
+      auto const node_index = ::communicator.calc_node_index();
+      auto ref_ks_local_size = 12 / ::communicator.node_grid;
+      if constexpr (FFTConfig::use_r2c) {
+        ref_ks_local_size[FFTConfig::r2c_dir] /= 2;
+        if (node_index[FFTConfig::r2c_dir] == 0) {
+          ref_ks_local_size[FFTConfig::r2c_dir] += 1;
+        }
+      }
+      BOOST_CHECK_EQUAL(fft.ks_local_size(), ref_ks_local_size);
+      BOOST_CHECK_EQUAL(fft.ks_local_ur_index() - fft.ks_local_ld_index(),
+                        ref_ks_local_size);
+    }
     // deactivate actor
     solver->detach_system(espresso::system);
     system.coulomb.impl->solver = std::nullopt;