From f6c59c9c2f0c05f626d13ebf8b708a2349fc21cd Mon Sep 17 00:00:00 2001
From: Matthew Shepherd <mashephe@indiana.edu>
Date: Wed, 2 Sep 2026 18:21:36 -0400
Subject: [PATCH 1/2] add comments to explain differences in standard and MPI
 implementations regarding loadMC()

---
 AmpTools/IUAmpTools/NormIntInterface.h         | 3 +--
 AmpTools/IUAmpToolsMPI/AmpToolsInterfaceMPI.cc | 2 ++
 AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc  | 9 ++-------
 AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h   | 2 --
 4 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/AmpTools/IUAmpTools/NormIntInterface.h b/AmpTools/IUAmpTools/NormIntInterface.h
index d702f155..7ddb1a24 100644
--- a/AmpTools/IUAmpTools/NormIntInterface.h
+++ b/AmpTools/IUAmpTools/NormIntInterface.h
@@ -91,8 +91,7 @@ class NormIntInterface
   
   void invalidateTerms();
 
-  // needs different implementations in MPI so make virtual
-  virtual void loadMC() const;
+  void loadMC() const;
 
 #endif
   
diff --git a/AmpTools/IUAmpToolsMPI/AmpToolsInterfaceMPI.cc b/AmpTools/IUAmpToolsMPI/AmpToolsInterfaceMPI.cc
index 91ee339c..28f69543 100644
--- a/AmpTools/IUAmpToolsMPI/AmpToolsInterfaceMPI.cc
+++ b/AmpTools/IUAmpToolsMPI/AmpToolsInterfaceMPI.cc
@@ -123,6 +123,8 @@ AmpToolsInterfaceMPI::AmpToolsInterfaceMPI(ConfigurationInfo* configurationInfo)
     NormIntInterface* normInt = NULL;
     if (genMCRdr && accMCRdr && intenMan && !(reaction->normIntFileInput())){
       normInt = new NormIntInterfaceMPI(genMCRdr, accMCRdr, *intenMan);
+      // no need to call loadMC() here because the constructor of 
+      // NormIntInterfaceMPI calls it through setupMPI()
       m_normIntMap[reactionName] = normInt;
       if (reaction->normIntFile() == "")
 	report( WARNING, kModule ) << "no name given to NormInt file for reaction "
diff --git a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
index a998f1b5..121d6a81 100644
--- a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
+++ b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
@@ -130,6 +130,8 @@ NormIntInterfaceMPI::setupMPI()
     
     // load the MC into CPU memory on the follower nodes -- this is effectively
     // a copy from the DataReaderMPI cache to the AmpVecs structure
+    // and it is only run on the followers to avoid large memory
+    // usage on the lead node
     loadMC();
 
     long int thisEvents;
@@ -202,10 +204,3 @@ NormIntInterfaceMPI::sumIntegrals( IntType type ) const
   delete[] result;
 }
 
-void
-NormIntInterfaceMPI::loadMC() const
-{
-  // avoids large memory allocations on the lead node
-  if( !m_isLeader ) NormIntInterface::loadMC();
-}
-
diff --git a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
index 3f450586..7abb9f0c 100644
--- a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
+++ b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
@@ -58,8 +58,6 @@ class NormIntInterfaceMPI : public NormIntInterface
   complex< double > normInt( string amp, string conjAmp, bool forceUseCache = false ) const;
   void forceCacheUpdate( bool normIntOnly = false ) const;
 
-  void loadMC() const;
-  
 private:
   
   void setupMPI();

From a74ec291a905b0ffdae5fd441c74f6d7d35672f3 Mon Sep 17 00:00:00 2001
From: Matthew Shepherd <mashephe@indiana.edu>
Date: Wed, 2 Sep 2026 19:21:12 -0400
Subject: [PATCH 2/2] introduce virtual loadMC to allow MPI implementation to
 avoid MC loads on the lead process

---
 AmpTools/IUAmpTools/NormIntInterface.h        | 2 +-
 AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc | 8 ++++++++
 AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h  | 2 ++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/AmpTools/IUAmpTools/NormIntInterface.h b/AmpTools/IUAmpTools/NormIntInterface.h
index 7ddb1a24..07e028d0 100644
--- a/AmpTools/IUAmpTools/NormIntInterface.h
+++ b/AmpTools/IUAmpTools/NormIntInterface.h
@@ -91,7 +91,7 @@ class NormIntInterface
   
   void invalidateTerms();
 
-  void loadMC() const;
+  virtual void loadMC() const;
 
 #endif
   
diff --git a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
index 121d6a81..70a9b911 100644
--- a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
+++ b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.cc
@@ -204,3 +204,11 @@ NormIntInterfaceMPI::sumIntegrals( IntType type ) const
   delete[] result;
 }
 
+void
+NormIntInterfaceMPI::loadMC() const{
+ 
+  // do not load MC on the leader node 
+  // only the followers need the MC
+  if( !m_isLeader ) NormIntInterface::loadMC();
+}
+
diff --git a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
index 7abb9f0c..067c047f 100644
--- a/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
+++ b/AmpTools/IUAmpToolsMPI/NormIntInterfaceMPI.h
@@ -58,6 +58,8 @@ class NormIntInterfaceMPI : public NormIntInterface
   complex< double > normInt( string amp, string conjAmp, bool forceUseCache = false ) const;
   void forceCacheUpdate( bool normIntOnly = false ) const;
 
+  void loadMC() const;
+
 private:
   
   void setupMPI();