ObserveTimeStep.hpp

// Distributed under the MIT License.
// See LICENSE.txt for details.
 
#pragma once
 
#include <cmath>
#include <cstddef>
#include <pup.h>
#include <pup_stl.h>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>
 
#include "IO/Observer/ArrayComponentId.hpp"
#include "IO/Observer/Helpers.hpp"
#include "IO/Observer/ObservationId.hpp"
#include "IO/Observer/ObserverComponent.hpp"  // IWYU pragma: keep
#include "IO/Observer/ReductionActions.hpp"   // IWYU pragma: keep
#include "IO/Observer/TypeOfObservation.hpp"
#include "Options/Options.hpp"
#include "Parallel/ArrayIndex.hpp"
#include "Parallel/CharmPupable.hpp"
#include "Parallel/GlobalCache.hpp"
#include "Parallel/Invoke.hpp"
#include "Parallel/Reduction.hpp"
#include "ParallelAlgorithms/EventsAndTriggers/Event.hpp"
#include "Time/Slab.hpp"
#include "Time/Time.hpp"
#include "Utilities/Functional.hpp"
#include "Utilities/Registration.hpp"
#include "Utilities/TMPL.hpp"
 
/// \cond
namespace Tags {
struct Time;
struct TimeStep;
}  // namespace Tags
/// \endcond
 
namespace Events {
/// \cond
template <typename Metavariables, typename EventRegistrars>
class ObserveTimeStep;
/// \endcond
 
namespace Registrars {
template <typename Metavariables>
using ObserveTimeStep =
    ::Registration::Registrar<Events::ObserveTimeStep, Metavariables>;
}  // namespace Registrars
 
/*!
 * \brief %Observe the size of the time steps.
 *
 * Writes reduction quantities:
 * - `%Time`
 * - `NumberOfPoints`
 * - `%Slab size`
 * - `Minimum time step`
 * - `Maximum time step`
 * - `Effective time step`
 *
 * The effective time step is the step size of a global-time-stepping
 * method that would perform a similar amount of work.  This is the
 * harmonic mean of the step size over all grid points:
 *
 * \f{equation}
 * (\Delta t)_{\text{eff}}^{-1} =
 * \frac{\sum_{i \in \text{points}} (\Delta t)_i^{-1}}{N_{\text{points}}}.
 * \f}
 *
 * This corresponds to averaging the number of steps per unit time
 * taken by all points.
 *
 * All values are reported as positive numbers, even for backwards
 * evolutions.
 */
template <typename Metavariables,
          typename EventRegistrars =
              tmpl::list<Registrars::ObserveTimeStep<Metavariables>>>
class ObserveTimeStep : public Event<EventRegistrars> {
 private:
  using ReductionData = Parallel::ReductionData<
      Parallel::ReductionDatum<double, funcl::AssertEqual<>>,
      Parallel::ReductionDatum<size_t, funcl::Plus<>>,
      Parallel::ReductionDatum<double, funcl::AssertEqual<>>,
      Parallel::ReductionDatum<double, funcl::Min<>>,
      Parallel::ReductionDatum<double, funcl::Max<>>,
      Parallel::ReductionDatum<
          double, funcl::Plus<>,
          funcl::Divides<funcl::Literal<1, double>, funcl::Divides<>>,
          std::index_sequence<1>>>;
 
 public:
  /// The name of the subfile inside the HDF5 file
  struct SubfileName {
    using type = std::string;
    static constexpr Options::String help = {
        "The name of the subfile inside the HDF5 file without an extension and "
        "without a preceding '/'."};
  };
 
  /// \cond
  explicit ObserveTimeStep(CkMigrateMessage* /*unused*/) noexcept {}
  using PUP::able::register_constructor;
  WRAPPED_PUPable_decl_template(ObserveTimeStep);  // NOLINT
  /// \endcond
 
  using options = tmpl::list<SubfileName>;
  static constexpr Options::String help =
      "Observe the size of the time steps.\n"
      "\n"
      "Writes reduction quantities:\n"
      "- Time\n"
      "- NumberOfPoints\n"
      "- Slab size\n"
      "- Minimum time step\n"
      "- Maximum time step\n"
      "- Effective time step\n"
      "\n"
      "The effective time step is the step size of a global-time-stepping\n"
      "method that would perform a similar amount of work.\n"
      "\n"
      "All values are reported as positive numbers, even for backwards\n"
      "evolutions.";
 
  ObserveTimeStep() = default;
  explicit ObserveTimeStep(const std::string& subfile_name) noexcept;
 
  using observed_reduction_data_tags =
      observers::make_reduction_data_tags<tmpl::list<ReductionData>>;
 
  // We obtain the grid size from the variables, rather than the mesh,
  // so that this observer is not DG-specific.
  using argument_tags =
      tmpl::list<Tags::Time, Tags::TimeStep,
                 typename Metavariables::system::variables_tag>;
 
  template <typename ArrayIndex, typename ParallelComponent>
  void operator()(
      const double& time, const TimeDelta& time_step,
      const typename Metavariables::system::variables_tag::type& variables,
      Parallel::GlobalCache<Metavariables>& cache,
      const ArrayIndex& array_index,
      const ParallelComponent* const /*meta*/) const noexcept {
    const size_t number_of_grid_points = variables.number_of_grid_points();
    const double slab_size = time_step.slab().duration().value();
    const double step_size = abs(time_step.value());
 
    auto& local_observer =
        *Parallel::get_parallel_component<observers::Observer<Metavariables>>(
             cache)
             .ckLocalBranch();
    Parallel::simple_action<observers::Actions::ContributeReductionData>(
        local_observer, observers::ObservationId(time, subfile_path_ + ".dat"),
        observers::ArrayComponentId{
            std::add_pointer_t<ParallelComponent>{nullptr},
            Parallel::ArrayIndex<ArrayIndex>(array_index)},
        subfile_path_,
        std::vector<std::string>{"Time", "NumberOfPoints", "Slab size",
                                 "Minimum time step", "Maximum time step",
                                 "Effective time step"},
        ReductionData{time, number_of_grid_points, slab_size, step_size,
                      step_size, number_of_grid_points / step_size});
  }
 
  using observation_registration_tags = tmpl::list<>;
  std::pair<observers::TypeOfObservation, observers::ObservationKey>
  get_observation_type_and_key_for_registration() const noexcept {
    return {observers::TypeOfObservation::Reduction,
            observers::ObservationKey(subfile_path_ + ".dat")};
  }
 
  // NOLINTNEXTLINE(google-runtime-references)
  void pup(PUP::er& p) override {
    Event<EventRegistrars>::pup(p);
    p | subfile_path_;
  }
 
 private:
  std::string subfile_path_;
};
 
template <typename Metavariables, typename EventRegistrars>
ObserveTimeStep<Metavariables, EventRegistrars>::ObserveTimeStep(
    const std::string& subfile_name) noexcept
    : subfile_path_("/" + subfile_name) {}
 
/// \cond
template <typename Metavariables, typename EventRegistrars>
PUP::able::PUP_ID ObserveTimeStep<Metavariables, EventRegistrars>::my_PUP_ID =
    0;  // NOLINT
/// \endcond
}  // namespace Events