Fix for passing of timestep

If a person implementing an interface with an MD code calls setMDTimeUnits after the call to
setTimestep then the timestep will not be in the correct units.  This fix resolves that problem.

src/core/Action.cpp

@@ -79,8 +79,7 @@ Action::Action(const ActionOptions&ao):
   keywords(ao.keys)
 {
   // Retrieve the timestep and save it
-  ActionWithValue* ts = plumed.getActionSet().selectWithLabel<ActionWithValue*>("timestep");
-  if( ts ) timestep = (ts->copyOutput(0))->get();
+  resetStoredTimestep();
 
   line.erase(line.begin());
   if( !keywords.exists("NO_ACTION_LOG") ) {
@@ -116,6 +115,11 @@ Action::Action(const ActionOptions&ao):
   }
 }
 
+void Action::resetStoredTimestep() {
+  ActionWithValue* ts = plumed.getActionSet().selectWithLabel<ActionWithValue*>("timestep");
+  if( ts ) timestep = (ts->copyOutput(0))->get();
+}
+
 Action::~Action() {
   if(files.size()!=0) {
     std::cerr<<"WARNING: some files open in action "+getLabel()+" where not properly closed. This could lead to data loss!!\n";

src/core/Action.h

@@ -329,6 +329,9 @@ class Action {
 /// Get the defaults
   std::string getDefaultString() const ;
 
+/// Set the timestep that is stored in the action to the correct value
+  void resetStoredTimestep();
+
 /// Get the info on what to calculate
   virtual std::string writeInGraph() const ;
 /// Specialized casts, to make PlumedMain run faster

src/core/PlumedMain.cpp

@@ -1406,6 +1406,7 @@ void PlumedMain::setUnits( const bool& natural, const Units& u ) {
   passtools->usingNaturalUnits = natural; passtools->units=u;
   std::vector<ActionToPutData*> idata = actionSet.select<ActionToPutData*>();
   for(const auto & ip : idata) ip->updateUnits( passtools.get() );
+  for(const auto & p : actionSet ) p->resetStoredTimestep();
 }
 
 void PlumedMain::startStep() {