From 418902a630a804c18a6b4513a6e2500c7787fbab Mon Sep 17 00:00:00 2001
From: Gareth Aneurin Tribello <garethtribello@Gareths-MacBook-Pro.local>
Date: Sun, 2 Jun 2024 10:35:02 +0100
Subject: [PATCH] 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     | 8 ++++++--
 src/core/Action.h       | 3 +++
 src/core/PlumedMain.cpp | 1 +
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/core/Action.cpp b/src/core/Action.cpp
index 27e3bb8272..0e1e24c8a4 100644
--- a/src/core/Action.cpp
+++ b/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";
diff --git a/src/core/Action.h b/src/core/Action.h
index eb6ba11b65..08a5172190 100644
--- a/src/core/Action.h
+++ b/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
diff --git a/src/core/PlumedMain.cpp b/src/core/PlumedMain.cpp
index 487650bd65..a5f888088d 100644
--- a/src/core/PlumedMain.cpp
+++ b/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() {