Switch to adapter-based checkpointing in the two-scale heat conduction tutorial (#676)

* Switch to DuMuX adapter checkpointing functionality

* Remove manual checkpointing of time as the adapter handles this internally

* Checkpoint timestepping

* Add changelog entry

* Move initialize() call before time settings

Author: IshaanDesai

changelog-entries/676.md

@@ -0,0 +1 @@
+- Switched to adapter-based checkpointing in the macro-dumux participant of the two-scale heat conduction tutorial [#676](https://github.com/precice/tutorials/pull/676)

two-scale-heat-conduction/macro-dumux/appl/main.cc

@@ -173,10 +173,6 @@ int main(int argc, char **argv)
   problem->applyInitialSolution(x);
   auto xOld = x;
 
-  auto   xCheckpoint        = x;
-  double timeCheckpoint     = 0.0;
-  int    timeStepCheckpoint = 0;
-
   // initialize the coupling data
   std::vector<double> temperatures;
   for (int solIdx = 0; solIdx < numberOfElements; ++solIdx) {
@@ -227,7 +223,9 @@ int main(int argc, char **argv)
   const int vtkOutputInterval = getParam<int>("TimeLoop.OutputInterval");
 
   // initialize preCICE
-  couplingParticipant.initialize();
+  if (runWithCoupling) {
+    couplingParticipant.initialize();
+  }
 
   // time loop parameters
   const auto tEnd      = getParam<Scalar>("TimeLoop.TEnd");
@@ -246,6 +244,11 @@ int main(int argc, char **argv)
   auto timeLoop = std::make_shared<TimeLoop<Scalar>>(0.0, dt, tEnd);
   timeLoop->setMaxTimeStepSize(getParam<Scalar>("TimeLoop.MaxDt"));
 
+  // initialize adapter checkpointing
+  if (runWithCoupling) {
+    couplingParticipant.initializeCheckpoint(x, *gridVariables, *timeLoop);
+  }
+
   // the assembler with time loop for instationary problem
   using Assembler = FVAssembler<TypeTag, DiffMethod::numeric>;
   auto assembler  = std::make_shared<Assembler>(problem, gridGeometry,
@@ -272,11 +275,7 @@ int main(int argc, char **argv)
         break;
 
       // write checkpoint
-      if (couplingParticipant.requiresToWriteCheckpoint()) {
-        xCheckpoint        = x;
-        timeCheckpoint     = timeLoop->time();
-        timeStepCheckpoint = timeLoop->timeStepIndex();
-      }
+      couplingParticipant.writeCheckpointIfRequired();
 
       preciceDt = couplingParticipant.getMaxTimeStepSize();
       solverDt  = std::min(nonLinearSolver.suggestTimeStepSize(timeLoop->timeStepSize()),
@@ -357,15 +356,9 @@ int main(int argc, char **argv)
       couplingParticipant.advance(dt);
 
       // reset to checkpoint if not converged
-      if (couplingParticipant.requiresToReadCheckpoint()) {
-        x    = xCheckpoint;
-        xOld = x;
-        timeLoop->setTime(timeCheckpoint, timeStepCheckpoint);
-
-        // TODO: previousTimeStep might be more appropriate, last one could be small
-        timeLoop->setTimeStepSize(dt);
-        gridVariables->update(x);
+      if (couplingParticipant.readCheckpointIfRequired()) {
         gridVariables->advanceTimeStep();
+        xOld = x;
         continue;
       }
     }