Have openmc_init take a MPI_Comm*

CMakeLists.txt

@@ -434,6 +434,7 @@ set(LIBOPENMC_FORTRAN_SRC
 )
 set(LIBOPENMC_CXX_SRC
   src/error.h
+  src/initialize.cpp
   src/hdf5_interface.h
   src/hdf5_interface.cpp
   src/random_lcg.cpp

include/openmc.h

@@ -4,6 +4,10 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#ifdef OPENMC_MPI
+#include "mpi.h"
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -46,7 +50,8 @@ extern "C" {
   int64_t openmc_get_seed();
   int openmc_get_tally_index(int32_t id, int32_t* index);
   void openmc_hard_reset();
-  void openmc_init(const int* intracomm);
+  int openmc_init(const void* intracomm);
+  int openmc_init_f(const int* intracomm);
   int openmc_legendre_filter_get_order(int32_t index, int* order);
   int openmc_legendre_filter_set_order(int32_t index, int order);
   int openmc_load_nuclide(char name[]);
@@ -145,6 +150,11 @@ extern "C" {
   extern bool openmc_simulation_initialized;
   extern int openmc_verbosity;
 
+#ifdef OPENMC_MPI
+  // MPI variables
+  extern MPI_Comm openmc_intracomm;
+#endif
+
   // Run modes
   constexpr int RUN_MODE_FIXEDSOURCE {1};
   constexpr int RUN_MODE_EIGENVALUE {2};

openmc/capi/core.py

@@ -1,6 +1,6 @@
 from contextlib import contextmanager
 from ctypes import (CDLL, c_int, c_int32, c_int64, c_double, c_char_p,
-                    POINTER, Structure)
+                    POINTER, Structure, c_void_p)
 from warnings import warn
 
 import numpy as np
@@ -27,7 +27,7 @@ _dll.openmc_find.argtypes = [POINTER(c_double*3), c_int, POINTER(c_int32),
 _dll.openmc_find.restype = c_int
 _dll.openmc_find.errcheck = _error_handler
 _dll.openmc_hard_reset.restype = None
-_dll.openmc_init.argtypes = [POINTER(c_int)]
+_dll.openmc_init.argtypes = [c_void_p]
 _dll.openmc_init.restype = None
 _dll.openmc_get_keff.argtypes = [POINTER(c_double*2)]
 _dll.openmc_get_keff.restype = c_int
@@ -116,13 +116,11 @@ def init(intracomm=None):
 
     """
     if intracomm is not None:
-        # If an mpi4py communicator was passed, convert it to an integer to
-        # be passed to openmc_init
-        try:
-            intracomm = intracomm.py2f()
-        except AttributeError:
-            pass
-        _dll.openmc_init(c_int(intracomm))
+        # If an mpi4py communicator was passed, convert it to void* to be passed
+        # to openmc_init
+        from mpi4py import MPI
+        address = MPI._addressof(intracomm)
+        _dll.openmc_init(c_void_p(address))
     else:
         _dll.openmc_init(None)
 

src/api.F90

@@ -15,7 +15,7 @@ module openmc_api
   use mesh_header
   use message_passing
   use nuclide_header
-  use initialize,      only: openmc_init
+  use initialize,      only: openmc_init_f
   use particle_header, only: Particle
   use plot,            only: openmc_plot_geometry
   use random_lcg,      only: openmc_get_seed, openmc_set_seed
@@ -64,7 +64,7 @@ module openmc_api
   public :: openmc_get_tally_index
   public :: openmc_global_tallies
   public :: openmc_hard_reset
-  public :: openmc_init
+  public :: openmc_init_f
   public :: openmc_load_nuclide
   public :: openmc_material_add_nuclide
   public :: openmc_material_get_id

src/hdf5_interface.cpp

@@ -1,14 +1,19 @@
 #include "hdf5_interface.h"
-#include "error.h"
-
-#include "hdf5.h"
-#include "hdf5_hl.h"
 
 #include <array>
 #include <cstring>
 #include <string>
 #include <sstream>
 
+#include "hdf5.h"
+#include "hdf5_hl.h"
+#ifdef OPENMC_MPI
+#include "mpi.h"
+#include "openmc.h"
+#endif
+#include "error.h"
+
+
 namespace openmc {
 
 bool
@@ -158,7 +163,7 @@ file_open(const char* filename, char mode, bool parallel)
   if (parallel) {
     // Setup file access property list with parallel I/O access
     plist = H5Pcreate(H5P_FILE_ACCESS);
-    H5Pset_fapl_mpio(plist, mpi_intracomm, MPI_INFO_NULL);
+    H5Pset_fapl_mpio(plist, openmc_intracomm, MPI_INFO_NULL);
   }
 #endif
 

src/initialize.F90

@@ -41,8 +41,9 @@ contains
 ! setting up timers, etc.
 !===============================================================================
 
-  subroutine openmc_init(intracomm) bind(C)
+  function openmc_init_f(intracomm) result(err) bind(C)
     integer, intent(in), optional :: intracomm  ! MPI intracommunicator
+    integer(C_INT) :: err
 
 #ifdef _OPENMP
     character(MAX_WORD_LEN) :: envvar
@@ -105,7 +106,8 @@ contains
     ! Stop initialization timer
     call time_initialize%stop()
 
-  end subroutine openmc_init
+    err = 0
+  end function openmc_init_f
 
 #ifdef OPENMC_MPI
 !===============================================================================

src/initialize.cpp

@@ -0,0 +1,20 @@
+#include "openmc.h"
+
+#ifdef OPENMC_MPI
+MPI_Comm openmc_intracomm;
+#endif
+
+
+int
+openmc_init(const void* intracomm)
+{
+#ifdef OPENMC_MPI
+  openmc_intracomm = *static_cast<const MPI_Comm *>(intracomm);
+
+  MPI_Fint fcomm = MPI_Comm_c2f(openmc_intracomm);
+  openmc_init_f(&fcomm);
+#else
+  openmc_init_f(nullptr);
+#endif
+  return 0;
+}

src/main.cpp

@@ -1,17 +1,15 @@
 #include "openmc.h"
 
-#ifdef MPI
-#include <mpi.h>
-#else
-#define MPI_COMM_WORLD nullptr
-#endif
-
-
 int main(int argc, char** argv) {
   int err;
 
   // Initialize run -- when run with MPI, pass communicator
-  openmc_init(MPI_COMM_WORLD);
+#ifdef OPENMC_MPI
+  MPI_Comm world {MPI_COMM_WORLD};
+  openmc_init(&world);
+#else
+  openmc_init(nullptr);
+#endif
 
   // start problem based on mode
   switch (openmc_run_mode) {