Add IMEX initialization mutator

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

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/CMakeLists.txt

@@ -5,6 +5,7 @@ set(LIBRARY "Test_Imex")
 
 set(LIBRARY_SOURCES
   Test_GuessResult.cpp
+  Test_Initialize.cpp
   Test_Mode.cpp
   Test_SolveImplicitSector.cpp
   )

tests/Unit/Evolution/Imex/Test_Initialize.cpp

@@ -0,0 +1,95 @@
+// Distributed under the MIT License.
+// See LICENSE.txt for details.
+
+#include "Framework/TestingFramework.hpp"
+
+#include "DataStructures/DataBox/DataBox.hpp"
+#include "DataStructures/DataBox/Prefixes.hpp"
+#include "DataStructures/DataBox/Tag.hpp"
+#include "DataStructures/DataVector.hpp"
+#include "DataStructures/Tensor/Tensor.hpp"
+#include "DataStructures/Tensor/TypeAliases.hpp"
+#include "DataStructures/Variables.hpp"
+#include "DataStructures/VariablesTag.hpp"
+#include "Evolution/Imex/GuessResult.hpp"
+#include "Evolution/Imex/Initialize.hpp"
+#include "Evolution/Imex/Protocols/ImexSystem.hpp"
+#include "Evolution/Imex/Protocols/ImplicitSector.hpp"
+#include "Evolution/Imex/Tags/ImplicitHistory.hpp"
+#include "Time/Tags/HistoryEvolvedVariables.hpp"
+#include "Utilities/Gsl.hpp"
+#include "Utilities/ProtocolHelpers.hpp"
+#include "Utilities/TMPL.hpp"
+
+namespace {
+template <typename Var>
+struct Sector : tt::ConformsTo<imex::protocols::ImplicitSector> {
+  using tensors = tmpl::list<Var>;
+
+  struct initial_guess {
+    using return_tags = tmpl::list<Var>;
+    using argument_tags = tmpl::list<>;
+    static imex::GuessResult apply(
+        gsl::not_null<Scalar<DataVector>*> var,
+        const Variables<tmpl::list<Var>>& inhomogeneous_terms,
+        double implicit_weight);
+  };
+
+  struct SolveAttempt {
+    struct source {
+      using return_tags = tmpl::list<Tags::Source<Var>>;
+      using argument_tags = tmpl::list<Var>;
+      static void apply(gsl::not_null<Scalar<DataVector>*> source);
+    };
+
+    using jacobian = imex::NoJacobianBecauseSolutionIsAnalytic;
+
+    using tags_from_evolution = tmpl::list<>;
+    using simple_tags = tmpl::list<>;
+    using compute_tags = tmpl::list<>;
+    using source_prep = tmpl::list<>;
+    using jacobian_prep = tmpl::list<>;
+  };
+  using solve_attempts = tmpl::list<SolveAttempt>;
+};
+
+struct Var1 : db::SimpleTag {
+  using type = Scalar<DataVector>;
+};
+
+struct Var2 : db::SimpleTag {
+  using type = Scalar<DataVector>;
+};
+
+struct System : tt::ConformsTo<imex::protocols::ImexSystem> {
+  using variables_tag = Tags::Variables<tmpl::list<Var1, Var2>>;
+  using implicit_sectors = tmpl::list<Sector<Var1>, Sector<Var2>>;
+};
+}  // namespace
+
+SPECTRE_TEST_CASE("Unit.Evolution.Imex.Initialize", "[Unit][Evolution]") {
+  using initialize_imex = imex::Initialize<System>;
+  using explicit_history_tag =
+      Tags::HistoryEvolvedVariables<System::variables_tag>;
+  auto box =
+      db::create<db::AddSimpleTags<System::variables_tag, explicit_history_tag,
+                                   initialize_imex::simple_tags>>();
+  db::mutate<System::variables_tag, explicit_history_tag>(
+      [](const gsl::not_null<System::variables_tag::type*> variables,
+         const gsl::not_null<explicit_history_tag::type*> explicit_history) {
+        variables->initialize(5);
+        explicit_history->integration_order(3);
+      },
+      make_not_null(&box));
+
+  db::mutate_apply<initialize_imex>(make_not_null(&box));
+
+  CHECK(db::get<imex::Tags::ImplicitHistory<Sector<Var1>>>(box)
+            .integration_order() == 3);
+  CHECK(db::get<imex::Tags::ImplicitHistory<Sector<Var2>>>(box)
+            .integration_order() == 3);
+  CHECK(db::get<imex::Tags::SolveFailures<Sector<Var1>>>(box) ==
+        Scalar<DataVector>(DataVector(5, 0.0)));
+  CHECK(db::get<imex::Tags::SolveFailures<Sector<Var2>>>(box) ==
+        Scalar<DataVector>(DataVector(5, 0.0)));
+}