Restructure device CKF for readability (#728)

This commit doesn't change the CKF much functionally, but improves its
readability a bit by moving variables closer to where they are used, and
by adding smaller scopes. Also increases the clarity of the double
buffering solution.

May decrease memory consumption slightly as it encourages the compiler
to free memory earlier.

device/common/CMakeLists.txt

@@ -20,7 +20,6 @@ traccc_add_library( traccc_device_common device_common TYPE SHARED
  "include/traccc/device/container_d2h_copy_alg.hpp"
  "include/traccc/device/impl/container_d2h_copy_alg.ipp"
  # EDM class(es).
- "include/traccc/edm/device/finding_global_counter.hpp"
  "include/traccc/edm/device/seeding_global_counter.hpp"
  "include/traccc/edm/device/doublet_counter.hpp"
  "include/traccc/edm/device/triplet_counter.hpp"

device/common/include/traccc/finding/device/impl/propagate_to_next_surface.ipp

@@ -17,13 +17,13 @@ TRACCC_DEVICE inline void propagate_to_next_surface(
  bound_track_parameters_collection_types::const_view in_params_view,
  const vecmem::data::vector_view<const unsigned int>& param_ids_view,
  vecmem::data::vector_view<const candidate_link> links_view,
- const unsigned int step, const unsigned int& n_in_params,
+ const unsigned int step, const unsigned int n_in_params,
  bound_track_parameters_collection_types::view out_params_view,
  vecmem::data::vector_view<unsigned int> param_to_link_view,
  vecmem::data::vector_view<typename candidate_link::link_index_type>
  tips_view,
  vecmem::data::vector_view<unsigned int> n_tracks_per_seed_view,
- unsigned int& n_out_params) {
+ unsigned int* n_out_params) {
 
  if (globalIndex >= n_in_params) {
  return;
@@ -116,7 +116,7 @@ TRACCC_DEVICE inline void propagate_to_next_surface(
 
  // If a surface found, add the parameter for the next step
  if (s4.success) {
- vecmem::device_atomic_ref<unsigned int> num_out_params(n_out_params);
+ vecmem::device_atomic_ref<unsigned int> num_out_params(*n_out_params);
  const unsigned int out_param_id = num_out_params.fetch_add(1);
 
  out_params[out_param_id] = propagation._stepping._bound_params;

device/common/include/traccc/finding/device/propagate_to_next_surface.hpp

@@ -44,13 +44,13 @@ TRACCC_DEVICE inline void propagate_to_next_surface(
  bound_track_parameters_collection_types::const_view in_params_view,
  const vecmem::data::vector_view<const unsigned int>& param_ids_view,
  vecmem::data::vector_view<const candidate_link> links_view,
- const unsigned int step, const unsigned int& n_in_params,
+ const unsigned int step, const unsigned int n_in_params,
  bound_track_parameters_collection_types::view out_params_view,
  vecmem::data::vector_view<unsigned int> param_to_link_view,
  vecmem::data::vector_view<typename candidate_link::link_index_type>
  tips_view,
  vecmem::data::vector_view<unsigned int> n_tracks_per_seed_view,
- unsigned int& n_out_params);
+ unsigned int* n_out_params);
 
 } // namespace traccc::device