Add IMEX actions

src/Evolution/Imex/Actions/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Distributed under the MIT License.
+# See LICENSE.txt for details.
+
+spectre_target_headers(
+  ${LIBRARY}
+  INCLUDE_DIRECTORY ${CMAKE_SOURCE_DIR}/src
+  HEADERS
+  DoImplicitStep.hpp
+  NamespaceDocs.hpp
+  RecordTimeStepperData.hpp
+  )

src/Evolution/Imex/Actions/DoImplicitStep.hpp

@@ -0,0 +1,90 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#pragma once
+
+#include <optional>
+
+#include "DataStructures/DataBox/DataBox.hpp"
+#include "Evolution/Imex/Protocols/ImexSystem.hpp"
+#include "Evolution/Imex/SolveImplicitSector.hpp"
+#include "Parallel/AlgorithmExecution.hpp"
+#include "Time/TimeStepId.hpp"
+#include "Utilities/CleanupRoutine.hpp"
+#include "Utilities/Gsl.hpp"
+#include "Utilities/ProtocolHelpers.hpp"
+#include "Utilities/TMPL.hpp"
+
+/// \cond
+namespace Parallel {
+template <typename Metavariables>
+class GlobalCache;
+}  // namespace Parallel
+namespace Tags {
+template <typename Tag>
+struct Next;
+struct Time;
+struct TimeStepId;
+}  // namespace Tags
+namespace db {
+template <typename TagsList>
+class DataBox;
+}  // namespace db
+namespace tuples {
+template <class... Tags>
+class TaggedTuple;
+}  // namespace tuples
+/// \endcond
+
+namespace imex::Actions {
+/// \ingroup ActionsGroup
+/// \brief Perform implicit variable updates for one substep
+///
+/// Uses:
+/// - DataBox:
+///   - Tags::Next<Tags::TimeStepId>
+///   - Tags::Time
+///   - Tags::TimeStep
+///   - Tags::TimeStepper<ImexTimeStepper>
+///   - imex::Tags::Mode
+///   - imex::Tags::SolveTolerance
+///   - as required by system implicit sectors
+///
+/// DataBox changes:
+/// - variables_tag
+/// - imex::Tags::ImplicitHistory<sector> for each sector
+template <typename System>
+struct DoImplicitStep {
+  template <typename DbTags, typename... InboxTags, typename Metavariables,
+            typename ArrayIndex, typename ActionList,
+            typename ParallelComponent>
+  static Parallel::iterable_action_return_t apply(
+      db::DataBox<DbTags>& box, tuples::TaggedTuple<InboxTags...>& /*inboxes*/,
+      const Parallel::GlobalCache<Metavariables>& /*cache*/,
+      const ArrayIndex& /*array_index*/, ActionList /*meta*/,
+      const ParallelComponent* const /*meta*/) {
+    static_assert(tt::assert_conforms_to_v<System, protocols::ImexSystem>);
+
+    const double original_time = db::get<::Tags::Time>(box);
+    const CleanupRoutine reset_time = [&]() {
+      db::mutate<::Tags::Time>(
+          [&](const gsl::not_null<double*> time) { *time = original_time; },
+          make_not_null(&box));
+    };
+    db::mutate<::Tags::Time>(
+        [](const gsl::not_null<double*> time,
+           const TimeStepId& next_time_step_id) {
+          *time = next_time_step_id.substep_time();
+        },
+        make_not_null(&box), db::get<::Tags::Next<::Tags::TimeStepId>>(box));
+
+    tmpl::for_each<typename System::implicit_sectors>([&](auto sector_v) {
+      using sector = tmpl::type_from<decltype(sector_v)>;
+      db::mutate_apply<
+          SolveImplicitSector<typename System::variables_tag, sector>>(
+          make_not_null(&box));
+    });
+    return {Parallel::AlgorithmExecution::Continue, std::nullopt};
+  }
+};
+}  // namespace imex::Actions

src/Evolution/Imex/Actions/NamespaceDocs.hpp

@@ -0,0 +1,7 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#pragma once
+
+/// Actions related to evolution using implicit-explicit time stepping.
+namespace imex::Actions {}

src/Evolution/Imex/Actions/RecordTimeStepperData.hpp

@@ -0,0 +1,102 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#pragma once
+
+#include <cstddef>
+#include <optional>
+
+#include "DataStructures/DataBox/DataBox.hpp"
+#include "DataStructures/DataBox/PrefixHelpers.hpp"
+#include "DataStructures/DataBox/Prefixes.hpp"
+#include "DataStructures/Variables.hpp"
+#include "Evolution/Imex/Protocols/ImexSystem.hpp"
+#include "Evolution/Imex/Tags/ImplicitHistory.hpp"
+#include "Parallel/AlgorithmExecution.hpp"
+#include "Utilities/Gsl.hpp"
+#include "Utilities/ProtocolHelpers.hpp"
+#include "Utilities/TMPL.hpp"
+
+/// \cond
+class TimeStepId;
+namespace Parallel {
+template <typename Metavariables>
+class GlobalCache;
+}  // namespace Parallel
+namespace Tags {
+struct TimeStepId;
+}  // namespace Tags
+namespace tuples {
+template <class... Tags>
+class TaggedTuple;
+}  // namespace tuples
+/// \endcond
+
+namespace imex::Actions {
+/// \ingroup ActionsGroup
+/// \brief Records the implicit sources in the implicit time stepper history.
+///
+/// Uses:
+/// - GlobalCache: nothing
+/// - DataBox:
+///   - Tags::TimeStepId
+///   - system::variables_tag
+///   - as required by source terms
+///
+/// DataBox changes:
+/// - imex::Tags::ImplicitHistory<sector> for each sector
+template <typename System>
+struct RecordTimeStepperData {
+  template <typename DbTags, typename... InboxTags, typename Metavariables,
+            typename ArrayIndex, typename ActionList,
+            typename ParallelComponent>
+  static Parallel::iterable_action_return_t apply(
+      db::DataBox<DbTags>& box, tuples::TaggedTuple<InboxTags...>& /*inboxes*/,
+      const Parallel::GlobalCache<Metavariables>& /*cache*/,
+      const ArrayIndex& /*array_index*/, ActionList /*meta*/,
+      const ParallelComponent* const /*meta*/) {  // NOLINT const
+    static_assert(tt::assert_conforms_to_v<System, protocols::ImexSystem>);
+
+    const size_t number_of_grid_points =
+        db::get<typename System::variables_tag>(box).number_of_grid_points();
+
+    tmpl::for_each<typename System::implicit_sectors>([&](auto sector_v) {
+      using sector = tmpl::type_from<decltype(sector_v)>;
+      using source =
+          typename tmpl::front<typename sector::solve_attempts>::source;
+      using history_tag = Tags::ImplicitHistory<sector>;
+      using DtSectorVars =
+          Variables<db::wrap_tags_in<::Tags::dt, typename sector::tensors>>;
+      db::mutate_apply<
+          tmpl::list<history_tag>,
+          tmpl::push_front<typename source::argument_tags, ::Tags::TimeStepId>>(
+          [&](const gsl::not_null<typename history_tag::type*> history,
+              const TimeStepId& time_step_id, const auto&... source_arguments) {
+            history->insert_in_place(
+                time_step_id, history_tag::type::no_value,
+                [&](const gsl::not_null<DtSectorVars*> source_result) {
+                  source_result->initialize(number_of_grid_points);
+                  tmpl::as_pack<typename source::return_tags>(
+                      [&](auto... source_tags) {
+                        // The history stores derivatives as
+                        // ::Tags::dt<Var>, but the source provides
+                        // ::Tags::Source<Var>.  Since the only
+                        // implicit equations we support are source
+                        // terms, these quantities are equal, but we
+                        // still need to make the types match.
+                        source::apply(
+                            make_not_null(
+                                &get<::Tags::dt<db::remove_tag_prefix<
+                                    tmpl::type_from<decltype(source_tags)>>>>(
+                                    *source_result))...,
+                            source_arguments...);
+                      });
+                });
+          },
+          make_not_null(&box));
+    });
+
+    return {Parallel::AlgorithmExecution::Continue, std::nullopt};
+  }
+};
+}  // namespace imex::Actions

src/Evolution/Imex/CMakeLists.txt

@@ -17,6 +17,7 @@ spectre_target_headers(
   INCLUDE_DIRECTORY ${CMAKE_SOURCE_DIR}/src
   HEADERS
   GuessResult.hpp
+  Initialize.hpp
   Mode.hpp
   NamespaceDocs.hpp
   SolveImplicitSector.hpp
@@ -36,5 +37,6 @@ target_link_libraries(
   Utilities
   )
 
+add_subdirectory(Actions)
 add_subdirectory(Protocols)
 add_subdirectory(Tags)

src/Evolution/Imex/Initialize.hpp

@@ -0,0 +1,57 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#pragma once
+
+#include "Evolution/Imex/Protocols/ImexSystem.hpp"
+#include "Evolution/Imex/Tags/ImplicitHistory.hpp"
+#include "Evolution/Imex/Tags/Mode.hpp"
+#include "Evolution/Imex/Tags/SolveFailures.hpp"
+#include "Evolution/Imex/Tags/SolveTolerance.hpp"
+#include "Time/History.hpp"
+#include "Time/Tags/HistoryEvolvedVariables.hpp"
+#include "Utilities/Gsl.hpp"
+#include "Utilities/MakeWithValue.hpp"
+#include "Utilities/ProtocolHelpers.hpp"
+#include "Utilities/TMPL.hpp"
+
+namespace imex {
+/// Create the IMEX structures and options.
+template <typename System, typename = typename System::implicit_sectors>
+struct Initialize;
+
+/// \cond
+template <typename System, typename... Sectors>
+struct Initialize<System, tmpl::list<Sectors...>> {
+  static_assert(tt::assert_conforms_to_v<System, protocols::ImexSystem>);
+
+  using example_tensor_tag =
+      tmpl::front<typename tmpl::front<tmpl::list<Sectors...>>::tensors>;
+
+  using const_global_cache_tags = tmpl::list<Tags::Mode, Tags::SolveTolerance>;
+  using mutable_global_cache_tags = tmpl::list<>;
+  using simple_tags_from_options = tmpl::list<>;
+  using simple_tags = tmpl::list<Tags::ImplicitHistory<Sectors>...,
+                                 Tags::SolveFailures<Sectors>...>;
+  using compute_tags = tmpl::list<>;
+
+  using return_tags = simple_tags;
+  using argument_tags =
+      tmpl::list<::Tags::HistoryEvolvedVariables<>, example_tensor_tag>;
+
+  static void apply(
+      const gsl::not_null<
+          typename Tags::ImplicitHistory<Sectors>::type*>... histories,
+      const gsl::not_null<
+          typename Tags::SolveFailures<Sectors>::type*>... solve_failures,
+      const TimeSteppers::History<typename System::variables_tag::type>&
+          explicit_history,
+      const typename example_tensor_tag::type& example_tensor) {
+    const auto order = explicit_history.integration_order();
+    expand_pack((histories->integration_order(order), 0)...);
+    expand_pack(*solve_failures = make_with_value<Scalar<DataVector>>(
+                    example_tensor, 0.0)...);
+  }
+};
+/// \endcond
+}  // namespace imex

tests/Unit/Evolution/Imex/Actions/CMakeLists.txt

@@ -0,0 +1,8 @@
+# Distributed under the MIT License.
+# See LICENSE.txt for details.
+
+set(LIBRARY_SOURCES
+  ${LIBRARY_SOURCES}
+  Actions/Test_DoImplicitStep.cpp
+  Actions/Test_RecordTimeStepperData.cpp
+  PARENT_SCOPE)