Use C bindings in MPI example

examples/extended/parallel/MPI/History

@@ -4,6 +4,10 @@ See `CONTRIBUTING.rst` for details of **required** info/format for each entry,
 which **must** added in reverse chronological order (newest at the top). It must **not**
 be used as a substitute for writing good git commit messages!
 
+## 2025-02-24 Filippo Falezza (MPI-V11-03-00)
+- Rewritten G4MPI to use C bindings (MPI 3+)
+  - Fixes [GitHub PR #81](https://github.com/Geant4/geant4/pull/81/)
+
 ## 2023-03-11 Ben Morgan (MPI-V11-02-00)
 - Move CTests definitions to tests/ctests_examples
 

examples/extended/parallel/MPI/README.md

@@ -27,9 +27,9 @@ http://www.open-mpi.org/
 MPI support:
 ------------
 G4mpi has been tested with the following MPI flavors:
- *   OpenMPI 1.8.1
- *   MPICH 3.2
- *   Intel MPI 5.0.1
+ *   OpenMPI 5.0.2 and 4.1.4
+ *   ~~MPICH 3.2~~
+ *   ~~Intel MPI 5.0.1~~
 
 ### CMake
 

examples/extended/parallel/MPI/examples/exMPI03/src/RunMerger.cc

@@ -32,14 +32,14 @@ void RunMerger::Pack()
 {
   // Very imporant, here fMyRun is const!
   // Register a user-data in the user Run class with MPI merger
-  InputUserData(const_cast<int*>(&(fMyRun->fDummyCounter)), MPI::INT, 1);
+  InputUserData(const_cast<int*>(&(fMyRun->fDummyCounter)), MPI_INT, 1);
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 G4Run* RunMerger::UnPack()
 {
   // Create a dummy user-Run, used to contain data received via MPI
   Run* aDummyRun = new Run;
-  OutputUserData(&(aDummyRun->fDummyCounter), MPI::INT, 1);
+  OutputUserData(&(aDummyRun->fDummyCounter), MPI_INT, 1);
   return aDummyRun;
 }

examples/extended/parallel/MPI/examples/exMPI04/src/RunMerger.cc

@@ -32,14 +32,14 @@ void RunMerger::Pack()
 {
   // Very imporant, here fMyRun is const!
   // Register a user-data in the user Run class with MPI merger
-  InputUserData(const_cast<int*>(&(fMyRun->fDummyCounter)), MPI::INT, 1);
+  InputUserData(const_cast<int*>(&(fMyRun->fDummyCounter)), MPI_INT, 1);
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 G4Run* RunMerger::UnPack()
 {
   // Create a dummy user-Run, used to contain data received via MPI
   Run* aDummyRun = new Run;
-  OutputUserData(&(aDummyRun->fDummyCounter), MPI::INT, 1);
+  OutputUserData(&(aDummyRun->fDummyCounter), MPI_INT, 1);
   return aDummyRun;
 }

examples/extended/parallel/MPI/source/include/G4MPImanager.hh

@@ -34,6 +34,7 @@
 
 #include <fstream>
 #include <pthread.h>
+#include <vector>
 
 #define DISALLOW_COPY_AND_ASSIGN(TypeName) \
   TypeName(const TypeName&);               \
@@ -123,11 +124,14 @@ class G4MPImanager
     // misc
     void ShowHelp() const;
 
-    const MPI::Intracomm* GetComm() const { return &COMM_G4COMMAND_; }
+    const MPI_Comm* GetComm() const { return &COMM_G4COMMAND_; }
     const MPI_Comm* GetProcessingComm() const { return &processing_comm_; }
     const MPI_Comm* GetCollectingComm() const { return &collecting_comm_; }
     const MPI_Comm* GetAllComm() const { return &all_comm_; }
 
+    std::vector<G4String> ReturnArguments() { return _options; }
+
+
   private:
     DISALLOW_COPY_AND_ASSIGN(G4MPImanager);
 
@@ -157,7 +161,7 @@ class G4MPImanager
     G4int world_size_;  // world comm size
 
     // MPI communicator (when no extra ranks)
-    MPI::Intracomm COMM_G4COMMAND_;
+    MPI_Comm COMM_G4COMMAND_;
     // MPI communicator (processing ranks - if ntuple merging)
     MPI_Comm processing_comm_;
     // MPI communicator (collecting ranks - if ntuple merging)
@@ -188,6 +192,8 @@ class G4MPImanager
     // parallel parameters
     G4double master_weight_;
     G4int nof_extra_workers_;
+
+    std::vector<G4String> _options;
 };
 
 // ====================================================================

examples/extended/parallel/MPI/source/include/G4MPIscorerMerger.hh

@@ -103,7 +103,7 @@ class G4MPIscorerMerger
     G4ScoringManager* scoringManager;
     unsigned int commSize;
     unsigned int destinationRank;
-    MPI::Intracomm comm;
+    MPI_Comm comm;
     G4int verbose;
 };
 

examples/extended/parallel/MPI/source/include/G4VUserMPIrunMerger.hh

@@ -50,16 +50,16 @@ class G4VUserMPIrunMerger
     virtual void Pack() = 0;
     virtual G4Run* UnPack() = 0;
 
-    void InputUserData(/*const*/ void* input_data, const MPI::Datatype& dt, int count)
+    void InputUserData(/*const*/ void* input_data, const MPI_Datatype& dt, int count)
     {
       input_userdata.push_back(const_registered_data{input_data, dt, count});
     }
-    void OutputUserData(void* input_data, const MPI::Datatype& dt, int count)
+    void OutputUserData(void* input_data, const MPI_Datatype& dt, int count)
     {
       output_userdata.push_back(registered_data{input_data, dt, count});
     }
 
-    // void GetUserData(void* output_data,const MPI::Datatype& dt, int count);
+    // void GetUserData(void* output_data,const MPI_Datatype& dt, int count);
 
     void SetupOutputBuffer(char* buff, G4int size, G4int position)
     {
@@ -91,7 +91,7 @@ class G4VUserMPIrunMerger
     unsigned int destinationRank;
     G4Run* run;
     unsigned int commSize;
-    MPI::Intracomm COMM_G4COMMAND_;
+    MPI_Comm COMM_G4COMMAND_;
     G4int verbose;
     long bytesSent;
 
@@ -103,7 +103,7 @@ class G4VUserMPIrunMerger
         // const_registered_data(const_registered_data&&) = default;
         // const_registered_data& operator=(const_registered_data&&) = default;
         /*const*/ void* p_data;
-        /*const*/ MPI::Datatype dt;
+        /*const*/ MPI_Datatype dt;
         /*const*/ int count;
     };
     std::vector<const_registered_data> input_userdata;
@@ -114,7 +114,7 @@ class G4VUserMPIrunMerger
         registered_data(const registered_data&) = default;
         registered_data& operator=(const registered_data&) = default;
         void* p_data;
-        /*const*/ MPI::Datatype dt;
+        /*const*/ MPI_Datatype dt;
         /*const*/ int count;
     };
     std::vector<registered_data> output_userdata;

examples/extended/parallel/MPI/source/src/G4MPIhistoMerger.cc

@@ -52,8 +52,9 @@ void G4MPIhistoMerger::Merge()
     G4cout << "Starting merging of histograms" << G4endl;
   }
 
-  const MPI::Intracomm* parentComm = G4MPImanager::GetManager()->GetComm();
-  MPI::Intracomm comm = parentComm->Dup();
+  const MPI_Comm* parentComm = G4MPImanager::GetManager()->GetComm();
+  MPI_Comm comm;
+  MPI_Comm_dup(*parentComm, &comm);
 
   G4bool verbose = (verboseLevel > 1);
   G4int tag = G4MPImanager::kTAG_HISTO;
@@ -68,5 +69,5 @@ void G4MPIhistoMerger::Merge()
   if (verboseLevel > 0) {
     G4cout << "End merging of histograms" << G4endl;
   }
-  comm.Free();
+  MPI_Comm_free(&comm);
 }