Consolidating number of threads and thread number queries into the openmp interface header (#2809)

include/openmc/openmp_interface.h

@@ -7,6 +7,27 @@
 
 namespace openmc {
 
+//==============================================================================
+//! Accessor functions related to number of threads and thread number
+//==============================================================================
+inline int num_threads()
+{
+#ifdef _OPENMP
+  return omp_get_max_threads();
+#else
+  return 1;
+#endif
+}
+
+inline int thread_num()
+{
+#ifdef _OPENMP
+  return omp_get_thread_num();
+#else
+  return 0;
+#endif
+}
+
 //==============================================================================
 //! An object used to prevent concurrent access to a piece of data.
 //

src/initialize.cpp

@@ -23,6 +23,7 @@
 #include "openmc/message_passing.h"
 #include "openmc/mgxs_interface.h"
 #include "openmc/nuclide.h"
+#include "openmc/openmp_interface.h"
 #include "openmc/output.h"
 #include "openmc/plot.h"
 #include "openmc/random_lcg.h"
@@ -63,13 +64,7 @@ int openmc_init(int argc, char* argv[], const void* intracomm)
     return err;
 
 #ifdef LIBMESH
-
-#ifdef _OPENMP
-  int n_threads = omp_get_max_threads();
-#else
-  int n_threads = 1;
-#endif
-
+  const int n_threads = num_threads();
   // initialize libMesh if it hasn't been initialized already
   // (if initialized externally, the libmesh_init object needs to be provided
   // also)

src/mesh.cpp

@@ -8,9 +8,7 @@
 #ifdef OPENMC_MPI
 #include "mpi.h"
 #endif
-#ifdef _OPENMP
-#include <omp.h>
-#endif
+
 #include "xtensor/xbuilder.hpp"
 #include "xtensor/xeval.hpp"
 #include "xtensor/xmath.hpp"
@@ -27,6 +25,7 @@
 #include "openmc/hdf5_interface.h"
 #include "openmc/memory.h"
 #include "openmc/message_passing.h"
+#include "openmc/openmp_interface.h"
 #include "openmc/random_dist.h"
 #include "openmc/search.h"
 #include "openmc/settings.h"
@@ -2715,13 +2714,7 @@ void LibMesh::initialize()
   libMesh::ExplicitSystem& eq_sys =
     equation_systems_->add_system<libMesh::ExplicitSystem>(eq_system_name_);
 
-#ifdef _OPENMP
-  int n_threads = omp_get_max_threads();
-#else
-  int n_threads = 1;
-#endif
-
-  for (int i = 0; i < n_threads; i++) {
+  for (int i = 0; i < num_threads(); i++) {
     pl_.emplace_back(m_->sub_point_locator());
     pl_.back()->set_contains_point_tol(FP_COINCIDENT);
     pl_.back()->enable_out_of_mesh_mode();
@@ -2896,13 +2889,7 @@ int LibMesh::get_bin(Position r) const
     return -1;
   }
 
-#ifdef _OPENMP
-  int thread_num = omp_get_thread_num();
-#else
-  int thread_num = 0;
-#endif
-
-  const auto& point_locator = pl_.at(thread_num);
+  const auto& point_locator = pl_.at(thread_num());
 
   const auto elem_ptr = (*point_locator)(p);
   return elem_ptr ? get_bin_from_element(elem_ptr) : -1;

src/plot.cpp

@@ -23,6 +23,7 @@
 #include "openmc/material.h"
 #include "openmc/mesh.h"
 #include "openmc/message_passing.h"
+#include "openmc/openmp_interface.h"
 #include "openmc/output.h"
 #include "openmc/particle.h"
 #include "openmc/progress_bar.h"
@@ -1218,11 +1219,7 @@ void ProjectionPlot::create_output() const
    * Note that a vector of vectors is required rather than a 2-tensor,
    * since the stack size varies within each column.
    */
-#ifdef _OPENMP
-  const int n_threads = omp_get_max_threads();
-#else
-  const int n_threads = 1;
-#endif
+  const int n_threads = num_threads();
   std::vector<std::vector<std::vector<TrackSegment>>> this_line_segments(
     n_threads);
   for (int t = 0; t < n_threads; ++t) {
@@ -1234,14 +1231,8 @@ void ProjectionPlot::create_output() const
 
 #pragma omp parallel
   {
-
-#ifdef _OPENMP
-    const int n_threads = omp_get_max_threads();
-    const int tid = omp_get_thread_num();
-#else
-    int n_threads = 1;
-    int tid = 0;
-#endif
+    const int n_threads = num_threads();
+    const int tid = thread_num();
 
     SourceSite s; // Where particle starts from (camera)
     s.E = 1;

src/volume_calc.cpp

@@ -10,18 +10,16 @@
 #include "openmc/message_passing.h"
 #include "openmc/mgxs_interface.h"
 #include "openmc/nuclide.h"
+#include "openmc/openmp_interface.h"
 #include "openmc/output.h"
 #include "openmc/random_lcg.h"
 #include "openmc/settings.h"
 #include "openmc/timer.h"
 #include "openmc/xml_interface.h"
 
-#include <fmt/core.h>
-#ifdef _OPENMP
-#include <omp.h>
-#endif
 #include "xtensor/xadapt.hpp"
 #include "xtensor/xview.hpp"
+#include <fmt/core.h>
 
 #include <algorithm> // for copy
 #include <cmath>     // for pow, sqrt
@@ -205,12 +203,7 @@ vector<VolumeCalculation::Result> VolumeCalculation::execute() const
       // At this point, each thread has its own pair of index/hits lists and we
       // now need to reduce them. OpenMP is not nearly smart enough to do this
       // on its own, so we have to manually reduce them
-
-#ifdef _OPENMP
-      int n_threads = omp_get_num_threads();
-#else
-      int n_threads = 1;
-#endif
+      const int n_threads = num_threads();
 
 #pragma omp for ordered schedule(static)
       for (int i = 0; i < n_threads; ++i) {