Redesign step/slab size changing

src/Evolution/Executables/Cce/CharacteristicExtractBase.hpp

@@ -14,7 +14,7 @@
 #include "NumericalAlgorithms/SpinWeightedSphericalHarmonics/SwshTags.hpp"
 #include "Time/StepChoosers/Constant.hpp"
 #include "Time/StepChoosers/ErrorControl.hpp"
-#include "Time/StepChoosers/Increase.hpp"
+#include "Time/StepChoosers/LimitIncrease.hpp"
 #include "Utilities/TMPL.hpp"
 
 template <bool EvolveCcm>
@@ -112,7 +112,7 @@ struct CharacteristicExtractDefaults {
                           tmpl::list<Cce::Tags::CauchyAngularCoords>>;
   using cce_step_choosers =
       tmpl::list<StepChoosers::Constant<StepChooserUse::LtsStep>,
-                 StepChoosers::Increase<StepChooserUse::LtsStep>,
+                 StepChoosers::LimitIncrease<StepChooserUse::LtsStep>,
                  StepChoosers::ErrorControl<StepChooserUse::LtsStep,
                                             Tags::Variables<evolved_swsh_tags>,
                                             swsh_vars_selector>,

src/Evolution/Executables/GeneralizedHarmonic/EvolveGhBinaryBlackHole.hpp

@@ -164,13 +164,8 @@
 #include "Time/Actions/UpdateU.hpp"
 #include "Time/ChangeSlabSize/Action.hpp"
 #include "Time/ChangeSlabSize/Tags.hpp"
-#include "Time/StepChoosers/Cfl.hpp"
-#include "Time/StepChoosers/Constant.hpp"
 #include "Time/StepChoosers/Factory.hpp"
-#include "Time/StepChoosers/Increase.hpp"
-#include "Time/StepChoosers/PreventRapidIncrease.hpp"
 #include "Time/StepChoosers/StepChooser.hpp"
-#include "Time/StepChoosers/StepToTimes.hpp"
 #include "Time/Tags/StepperErrors.hpp"
 #include "Time/Tags/Time.hpp"
 #include "Time/Tags/TimeStepId.hpp"

src/Evolution/Executables/GeneralizedHarmonic/GeneralizedHarmonicBase.hpp

@@ -131,13 +131,8 @@
 #include "Time/Actions/RecordTimeStepperData.hpp"
 #include "Time/Actions/SelfStartActions.hpp"
 #include "Time/Actions/UpdateU.hpp"
-#include "Time/StepChoosers/Cfl.hpp"
-#include "Time/StepChoosers/Constant.hpp"
 #include "Time/StepChoosers/Factory.hpp"
-#include "Time/StepChoosers/Increase.hpp"
-#include "Time/StepChoosers/PreventRapidIncrease.hpp"
 #include "Time/StepChoosers/StepChooser.hpp"
-#include "Time/StepChoosers/StepToTimes.hpp"
 #include "Time/Tags/Time.hpp"
 #include "Time/TimeSequence.hpp"
 #include "Time/TimeSteppers/Factory.hpp"

src/Evolution/Executables/GrMhd/GhValenciaDivClean/GhValenciaDivCleanBase.hpp

@@ -221,13 +221,8 @@
 #include "Time/Actions/SelfStartActions.hpp"  // IWYU pragma: keep
 #include "Time/Actions/UpdateU.hpp"
 #include "Time/ChangeSlabSize/Action.hpp"
-#include "Time/StepChoosers/Cfl.hpp"
-#include "Time/StepChoosers/Constant.hpp"
 #include "Time/StepChoosers/Factory.hpp"
-#include "Time/StepChoosers/Increase.hpp"
-#include "Time/StepChoosers/PreventRapidIncrease.hpp"
 #include "Time/StepChoosers/StepChooser.hpp"
-#include "Time/StepChoosers/StepToTimes.hpp"
 #include "Time/Tags/Time.hpp"
 #include "Time/Tags/TimeStepId.hpp"
 #include "Time/TimeSequence.hpp"

src/Evolution/Executables/ScalarTensor/ScalarTensorBase.hpp

@@ -132,13 +132,8 @@
 #include "Time/Actions/RecordTimeStepperData.hpp"
 #include "Time/Actions/SelfStartActions.hpp"
 #include "Time/Actions/UpdateU.hpp"
-#include "Time/StepChoosers/Cfl.hpp"
-#include "Time/StepChoosers/Constant.hpp"
 #include "Time/StepChoosers/Factory.hpp"
-#include "Time/StepChoosers/Increase.hpp"
-#include "Time/StepChoosers/PreventRapidIncrease.hpp"
 #include "Time/StepChoosers/StepChooser.hpp"
-#include "Time/StepChoosers/StepToTimes.hpp"
 #include "Time/Tags/Time.hpp"
 #include "Time/TimeSequence.hpp"
 #include "Time/TimeSteppers/Factory.hpp"

src/Evolution/Initialization/Evolution.hpp

@@ -26,6 +26,7 @@
 #include "Parallel/Tags/ArrayIndex.hpp"
 #include "ParallelAlgorithms/Amr/Protocols/Projector.hpp"
 #include "Time/AdaptiveSteppingDiagnostics.hpp"
+#include "Time/ChangeSlabSize/Tags.hpp"
 #include "Time/ChooseLtsStepSize.hpp"
 #include "Time/Slab.hpp"
 #include "Time/StepChoosers/StepChooser.hpp"
@@ -114,7 +115,8 @@ struct TimeStepping {
   /// Tags for items in the DataBox that are mutated by the apply function
   using return_tags =
       tmpl::list<::Tags::Next<::Tags::TimeStepId>, ::Tags::TimeStep,
-                 ::Tags::Next<::Tags::TimeStep>>;
+                 ::Tags::Next<::Tags::TimeStep>,
+                 ::Tags::ChangeSlabSize::SlabSizeGoal>;
 
   /// Tags for mutable DataBox items that are either default initialized or
   /// initialized by the apply function
@@ -130,6 +132,7 @@ struct TimeStepping {
   static void apply(const gsl::not_null<TimeStepId*> next_time_step_id,
                     const gsl::not_null<TimeDelta*> time_step,
                     const gsl::not_null<TimeDelta*> next_time_step,
+                    const gsl::not_null<double*> slab_size_goal,
                     const double initial_time_value,
                     const double initial_dt_value,
                     const double initial_slab_size,
@@ -141,13 +144,16 @@ struct TimeStepping {
                                   time_runs_forward, time_stepper);
     *time_step = choose_lts_step_size(initial_time, initial_dt_value);
     *next_time_step = *time_step;
+    *slab_size_goal =
+        time_runs_forward ? initial_slab_size : -initial_slab_size;
   }
 
   /// Given the items fetched from a DataBox by the argument_tags, when not
   /// using LTS, mutate the items in the DataBox corresponding to return_tags
   static void apply(const gsl::not_null<TimeStepId*> next_time_step_id,
                     const gsl::not_null<TimeDelta*> time_step,
                     const gsl::not_null<TimeDelta*> next_time_step,
+                    const gsl::not_null<double*> slab_size_goal,
                     const double initial_time_value,
                     const double initial_dt_value,
                     const double initial_slab_size,
@@ -159,6 +165,8 @@ struct TimeStepping {
                                   time_runs_forward, time_stepper);
     *time_step = (time_runs_forward ? 1 : -1) * initial_time.slab().duration();
     *next_time_step = *time_step;
+    *slab_size_goal =
+        time_runs_forward ? initial_slab_size : -initial_slab_size;
   }
 };
 
@@ -168,7 +176,8 @@ struct ProjectTimeStepping : tt::ConformsTo<amr::protocols::Projector> {
   using return_tags =
       tmpl::list<::Tags::TimeStepId, ::Tags::Next<::Tags::TimeStepId>,
                  ::Tags::TimeStep, ::Tags::Next<::Tags::TimeStep>, ::Tags::Time,
-                 ::Tags::AdaptiveSteppingDiagnostics>;
+                 ::Tags::AdaptiveSteppingDiagnostics,
+                 ::Tags::ChangeSlabSize::SlabSizeGoal>;
   using argument_tags = tmpl::list<Parallel::Tags::ArrayIndex>;
 
   static void apply(
@@ -179,6 +188,7 @@ struct ProjectTimeStepping : tt::ConformsTo<amr::protocols::Projector> {
       const gsl::not_null<double*> /*time*/,
       const gsl::not_null<AdaptiveSteppingDiagnostics*>
       /*adaptive_stepping_diagnostics*/,
+      const gsl::not_null<double*> /*slab_size_goal*/,
       const ElementId<Dim>& /*element_id*/,
       const std::pair<Mesh<Dim>, Element<Dim>>& /*old_mesh_and_element*/) {
     // Do not change anything for p-refinement
@@ -192,13 +202,15 @@ struct ProjectTimeStepping : tt::ConformsTo<amr::protocols::Projector> {
                     const gsl::not_null<double*> time,
                     const gsl::not_null<AdaptiveSteppingDiagnostics*>
                         adaptive_stepping_diagnostics,
+                    const gsl::not_null<double*> slab_size_goal,
                     const ElementId<Dim>& element_id,
                     const tuples::TaggedTuple<Tags...>& parent_items) {
     *time_step_id = get<::Tags::TimeStepId>(parent_items);
     *next_time_step_id = get<::Tags::Next<::Tags::TimeStepId>>(parent_items);
     *time_step = get<::Tags::TimeStep>(parent_items);
     *next_time_step = get<::Tags::Next<::Tags::TimeStep>>(parent_items);
     *time = get<::Tags::Time>(parent_items);
+    *slab_size_goal = get<::Tags::ChangeSlabSize::SlabSizeGoal>(parent_items);
 
     // Since AdaptiveSteppingDiagnostics are reduced over all elements, we
     // set the slab quantities to the same value over all children, and the
@@ -229,6 +241,7 @@ struct ProjectTimeStepping : tt::ConformsTo<amr::protocols::Projector> {
       const gsl::not_null<double*> time,
       const gsl::not_null<AdaptiveSteppingDiagnostics*>
           adaptive_stepping_diagnostics,
+      const gsl::not_null<double*> slab_size_goal,
       const ElementId<Dim>& /*element_id*/,
       const std::unordered_map<ElementId<Dim>, tuples::TaggedTuple<Tags...>>&
           children_items) {
@@ -248,6 +261,8 @@ struct ProjectTimeStepping : tt::ConformsTo<amr::protocols::Projector> {
     *time_step = get<::Tags::TimeStep>(slowest_child_items);
     *next_time_step = get<::Tags::Next<::Tags::TimeStep>>(slowest_child_items);
     *time = get<::Tags::Time>(slowest_child_items);
+    *slab_size_goal =
+        get<::Tags::ChangeSlabSize::SlabSizeGoal>(slowest_child_items);
     const auto& slowest_child_diagnostics =
         get<::Tags::AdaptiveSteppingDiagnostics>(slowest_child_items);
 

src/Time/Actions/ChangeStepSize.hpp

@@ -15,6 +15,7 @@
 #include "Time/ChooseLtsStepSize.hpp"
 #include "Time/Tags/AdaptiveSteppingDiagnostics.hpp"
 #include "Time/Tags/HistoryEvolvedVariables.hpp"
+#include "Time/TimeStepRequestProcessor.hpp"
 #include "Time/TimeSteppers/LtsTimeStepper.hpp"
 #include "Utilities/ErrorHandling/Assert.hpp"
 #include "Utilities/Gsl.hpp"
@@ -61,6 +62,20 @@ bool change_step_size(const gsl::not_null<db::DataBox<DbTags>*> box) {
 
   const auto& time_step_id = db::get<Tags::TimeStepId>(*box);
   ASSERT(time_step_id.substep() == 0, "Can't change step size on a substep.");
+
+  const auto& current_step = db::get<Tags::TimeStep>(*box);
+  const double last_step_size = current_step.value();
+
+  TimeStepRequestProcessor step_requests(time_step_id.time_runs_forward());
+  bool step_accepted = true;
+  for (const auto& step_chooser : step_choosers) {
+    const auto [step_request, step_choice_accepted] =
+        step_chooser->template desired_step<StepChoosersToUse>(last_step_size,
+                                                               *box);
+    step_requests.process(step_request);
+    step_accepted = step_accepted and step_choice_accepted;
+  }
+
   using history_tags = ::Tags::get_all_history_tags<DbTags>;
   bool can_change_step_size = true;
   tmpl::for_each<history_tags>([&box, &can_change_step_size, &time_stepper,
@@ -74,28 +89,14 @@ bool change_step_size(const gsl::not_null<db::DataBox<DbTags>*> box) {
         time_stepper.can_change_step_size(time_step_id, history);
   });
   if (not can_change_step_size) {
+    step_requests.error_on_hard_limit(
+        current_step.value(),
+        (time_step_id.step_time() + current_step).value());
     return true;
   }
 
-  const auto& current_step = db::get<Tags::TimeStep>(*box);
-
-  const double last_step_size = std::abs(db::get<Tags::TimeStep>(*box).value());
-
-  // The step choosers return the magnitude of the desired step, so
-  // we always want the minimum requirement, but we have to negate
-  // the final answer if time is running backwards.
-  double desired_step = std::numeric_limits<double>::infinity();
-  bool step_accepted = true;
-  for (const auto& step_chooser : step_choosers) {
-    const auto [step_choice, step_choice_accepted] =
-        step_chooser->template desired_step<StepChoosersToUse>(
-            last_step_size, *box);
-    desired_step = std::min(desired_step, step_choice);
-    step_accepted = step_accepted and step_choice_accepted;
-  }
-  if (not current_step.is_positive()) {
-    desired_step = -desired_step;
-  }
+  const double desired_step = step_requests.step_size(
+      time_step_id.step_time().value(), current_step.value());
 
   constexpr double smallest_relative_step_size = 1.0e-9;
   if (abs(desired_step / current_step.slab().duration().value()) <
@@ -124,6 +125,9 @@ bool change_step_size(const gsl::not_null<db::DataBox<DbTags>*> box) {
   // if step accepted, just proceed. Otherwise, change Time::Next and jump
   // back to the first instance of `UpdateU`.
   if (step_accepted) {
+    step_requests.error_on_hard_limit(
+        current_step.value(),
+        (time_step_id.step_time() + current_step).value());
     return true;
   } else {
     db::mutate<Tags::Next<Tags::TimeStepId>, Tags::TimeStep>(

src/Time/CMakeLists.txt

@@ -20,6 +20,8 @@ spectre_target_sources(
   Time.cpp
   TimeSequence.cpp
   TimeStepId.cpp
+  TimeStepRequest.cpp
+  TimeStepRequestProcessor.cpp
   Utilities.cpp
   )
 
@@ -42,6 +44,8 @@ spectre_target_headers(
   Time.hpp
   TimeSequence.hpp
   TimeStepId.hpp
+  TimeStepRequest.hpp
+  TimeStepRequestProcessor.hpp
   Utilities.hpp
   )