Fix time stepping behavior of KnoFuInterface

When a simulation end time coincided with a boundary condition change,
the solver would take one more step because the current time was less
than the final time.

Add a unit test case which covers the desired behavior.

dune/dorie/common/time_controller.hh

@@ -132,8 +132,15 @@ public:
 			// time has advanced after calculation
 			time += dt;
 
-			if(time >= tEnd-eps) // Simulation has ended. Do nothing
+			// Simulation has ended. Do nothing
+			if (time > tEnd) {
 				return true;
+			}
+			// NOTE: Simulation needs to know that we are actually at the end
+			else if (time <= tEnd && time >= tEnd-eps) {
+				time = tEnd;
+				return true;
+			}
 
 			dt = std::max(dt,dtmin);
 			dt = std::min(dt*dtinc,dtmax);
@@ -145,18 +152,19 @@ public:
 				changeTime = tsc.getNextTimeStamp(time);
 			}
 
-			if(changeTime < 0.0 && time+dt > tEnd){
-				// time step adjustment to tEnd
-				dt = tEnd-time;
-				_log->trace("Adjusting time step to simulation end at: {:.2e}",
-							tEnd);
-			}
-			else if(changeTime > 0.0 && time+dt >= changeTime){
+			if(changeTime > 0.0 && time+dt >= changeTime){
 				// time step adjustment to BC Change
 				dt = changeTime-time-eps;
 				_log->trace("Adapting time step to change in boundary condition at "
 					   		"{:.2e}", changeTime);
 			}
+
+			if(time+dt > tEnd){
+				// time step adjustment to tEnd
+				dt = tEnd-time;
+				_log->trace("Adjusting time step to simulation end at: {:.2e}",
+							tEnd);
+			}
 		}
 
 		else 	// Newton solver threw error. Time is not advanced

dune/dorie/test/test-knofu-interface-richards.bcdat

+spatial_resolution_north 0
+spatial_resolution_south 0
+spatial_resolution_west -1
+spatial_resolution_east -1
+number_BC_change_times 2
+0 neumann 0 dirichlet 0
+1000 neumann 0 dirichlet 0

dune/dorie/test/test-knofu-interface-richards.cc

@@ -115,6 +115,34 @@ void verify_position_vector (const Sim& sim,
     }
 }
 
+/// Run the simulation in the specified time frame and assert the final time
+template<typename Sim>
+bool check_time_stepping (Sim& sim,
+                          const double time_begin,
+                          const double time_end)
+{
+    sim.set_propagation_times(time_begin, time_end);
+    sim.run();
+    return Dune::FloatCmp::eq(sim.current_time(), time_end);
+}
+
+/// Check if the simulation beforms the expected time stepping
+template<typename Sim>
+void test_sim_time (Sim& sim)
+{
+    const double time_begin = 0.0;
+
+    // perform the first step to t=500
+    assert(check_time_stepping(sim, time_begin, 500.0));
+
+    // perform another step from t=0 to t=1000, where the BC changes
+    const auto time_bc_change = 1000.0;
+    assert(check_time_stepping(sim, time_begin, time_bc_change));
+
+    // perform final step to t=1500
+    assert(check_time_stepping(sim, time_bc_change, 1500.0));
+}
+
 int main(int argc, char** argv)
 {
   try{
@@ -166,6 +194,11 @@ int main(int argc, char** argv)
         log->info("Testing the state position vector");
         verify_position_vector(sim_1, grid);
 
+        log->info("Performing the time step test");
+        Dune::Dorie::KnoFuInterface<Traits> sim_3(inifile, gc, helper,
+            Dune::Dorie::FilterSolutionType::matric_head);
+        test_sim_time(sim_3);
+
         return 0;
     }
     catch (Dune::Exception &e){

dune/dorie/test/test-knofu-interface-richards.mini.in

 include ${CMAKE_BINARY_DIR}/doc/default_files/config.ini
 
 __name = sand, silt | expand medium
-_asset_path = "${PROJECT_SOURCE_DIR}/test"
 
 [grid]
 dimensions = 2
@@ -16,7 +15,10 @@ volume = 0, 1 | expand medium
 
 [richards]
 
-boundary.file = "{_asset_path}/bcs/infiltration_2d.dat"
+output.logLevel = trace
+time.startTimestep = 500
+
+boundary.file = "${CMAKE_CURRENT_LIST_DIR}/test-knofu-interface-richards.bcdat"
 
 parameters.file = test-param-richards-unscaled.yml