Remove thread_id and n_threads global variables

docs/source/io_formats/settings.rst

@@ -730,15 +730,6 @@ sections.
 
   *Default*: 10 K
 
----------------------
-``<threads>`` Element
----------------------
-
-The ``<threads>`` element indicates the number of OpenMP threads to be used for
-a simulation. It has no attributes and accepts a positive integer value.
-
-  *Default*: None (Determined by environment variable :envvar:`OMP_NUM_THREADS`)
-
 .. _trace:
 
 -------------------

include/openmc/simulation.h

@@ -44,12 +44,8 @@ extern std::vector<int64_t> work_index;
 
 // Threadprivate variables
 extern "C" bool trace;     //!< flag to show debug information
-#ifdef _OPENMP
-extern "C" int n_threads;  //!< number of OpenMP threads
-extern "C" int thread_id;  //!< ID of a given thread
-#endif
 
-#pragma omp threadprivate(current_work, thread_id, trace)
+#pragma omp threadprivate(current_work, trace)
 
 } // namespace simulation
 

openmc/settings.py

@@ -130,8 +130,6 @@ class Settings(object):
         range. 'multipole' is a boolean indicating whether or not the windowed
         multipole method should be used to evaluate resolved resonance cross
         sections.
-    threads : int
-        Number of OpenMP threads
     trace : tuple or list
         Show detailed information about a single particle, indicated by three
         integers: the batch number, generation number, and particle number
@@ -197,7 +195,6 @@ class Settings(object):
         self._statepoint = {}
         self._sourcepoint = {}
 
-        self._threads = None
         self._no_reduce = None
 
         self._verbosity = None
@@ -312,10 +309,6 @@ class Settings(object):
     def statepoint(self):
         return self._statepoint
 
-    @property
-    def threads(self):
-        return self._threads
-
     @property
     def no_reduce(self):
         return self._no_reduce
@@ -623,12 +616,6 @@ class Settings(object):
 
         self._temperature = temperature
 
-    @threads.setter
-    def threads(self, threads):
-        cv.check_type('number of threads', threads, Integral)
-        cv.check_greater_than('number of threads', threads, 0)
-        self._threads = threads
-
     @trace.setter
     def trace(self, trace):
         cv.check_type('trace', trace, Iterable, Integral)
@@ -885,11 +872,6 @@ class Settings(object):
                 else:
                     element.text = str(value)
 
-    def _create_threads_subelement(self, root):
-        if self._threads is not None:
-            element = ET.SubElement(root, "threads")
-            element.text = str(self._threads)
-
     def _create_trace_subelement(self, root):
         if self._trace is not None:
             element = ET.SubElement(root, "trace")
@@ -980,7 +962,6 @@ class Settings(object):
         self._create_entropy_mesh_subelement(root_element)
         self._create_trigger_subelement(root_element)
         self._create_no_reduce_subelement(root_element)
-        self._create_threads_subelement(root_element)
         self._create_verbosity_subelement(root_element)
         self._create_tabular_legendre_subelements(root_element)
         self._create_temperature_subelements(root_element)

src/bank.cpp

@@ -31,7 +31,7 @@ std::vector<Particle::Bank> master_fission_bank;
 void free_memory_bank()
 {
   simulation::source_bank.clear();
-#pragma omp parallel
+  #pragma omp parallel
   {
     simulation::fission_bank.clear();
   }

src/eigenvalue.cpp

@@ -20,6 +20,10 @@
 #include "openmc/timer.h"
 #include "openmc/tallies/tally.h"
 
+#ifdef _OPENMP
+#include <omp.h>
+#endif
+
 #include <algorithm> // for min
 #include <array>
 #include <cmath> // for sqrt, abs, pow
@@ -348,11 +352,13 @@ void calculate_average_keff()
 #ifdef _OPENMP
 void join_bank_from_threads()
 {
+  int n_threads = omp_get_max_threads();
+
   #pragma omp parallel
   {
     // Copy thread fission bank sites to one shared copy
     #pragma omp for ordered schedule(static)
-    for (int i = 0; i < simulation::n_threads; ++i) {
+    for (int i = 0; i < n_threads; ++i) {
       #pragma omp ordered
       {
         std::copy(
@@ -367,7 +373,7 @@ void join_bank_from_threads()
     #pragma omp barrier
 
     // Now copy the shared fission bank sites back to the master thread's copy.
-    if (simulation::thread_id == 0) {
+    if (omp_get_thread_num() == 0) {
       simulation::fission_bank = simulation::master_fission_bank;
       simulation::master_fission_bank.clear();
     } else {

src/initialize.cpp

@@ -196,13 +196,13 @@ parse_command_line(int argc, char* argv[])
 
 #ifdef _OPENMP
         // Read and set number of OpenMP threads
-        simulation::n_threads = std::stoi(argv[i]);
-        if (simulation::n_threads < 1) {
+        int n_threads = std::stoi(argv[i]);
+        if (n_threads < 1) {
           std::string msg {"Number of threads must be positive."};
           strcpy(openmc_err_msg, msg.c_str());
           return OPENMC_E_INVALID_ARGUMENT;
         }
-        omp_set_num_threads(simulation::n_threads);
+        omp_set_num_threads(n_threads);
 #else
         if (mpi::master)
           warning("Ignoring number of threads specified on command line.");

src/output.cpp

@@ -11,7 +11,9 @@
 #include <unordered_map>
 #include <utility> // for pair
 
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 #include "xtensor/xview.hpp"
 
 #include "openmc/capi.h"

src/particle.cpp

@@ -590,7 +590,7 @@ Particle::mark_as_lost(const char* message)
 
   // Increment number of lost particles
   alive_ = false;
-#pragma omp atomic
+  #pragma omp atomic
   simulation::n_lost_particles += 1;
 
   // Count the total number of simulated particles (on this processor)
@@ -615,7 +615,7 @@ Particle::write_restart() const
   filename << settings::path_output << "particle_" << simulation::current_batch
     << '_' << id_ << ".h5";
 
-#pragma omp critical (WriteParticleRestart)
+  #pragma omp critical (WriteParticleRestart)
   {
     // Create file
     hid_t file_id = file_open(filename.str(), 'w');

src/physics_mg.cpp

@@ -174,22 +174,19 @@ absorption(Particle* p)
 {
   if (settings::survival_biasing) {
     // Determine weight absorbed in survival biasing
-    p->wgt_absorb_ = p->wgt_ *
-         p->macro_xs_.absorption / p->macro_xs_.total;
+    p->wgt_absorb_ = p->wgt_ * p->macro_xs_.absorption / p->macro_xs_.total;
 
     // Adjust weight of particle by the probability of absorption
     p->wgt_ -= p->wgt_absorb_;
     p->wgt_last_ = p->wgt_;
 
     // Score implicit absorpion estimate of keff
-#pragma omp atomic
-    global_tally_absorption += p->wgt_absorb_ *
-         p->macro_xs_.nu_fission /
-         p->macro_xs_.absorption;
+    #pragma omp atomic
+    global_tally_absorption += p->wgt_absorb_ * p->macro_xs_.nu_fission /
+        p->macro_xs_.absorption;
   } else {
-    if (p->macro_xs_.absorption >
-        prn() * p->macro_xs_.total) {
-#pragma omp atomic
+    if (p->macro_xs_.absorption > prn() * p->macro_xs_.total) {
+      #pragma omp atomic
       global_tally_absorption += p->wgt_ * p->macro_xs_.nu_fission /
            p->macro_xs_.absorption;
       p->alive_ = false;

src/random_lcg.cpp

@@ -141,7 +141,7 @@ extern "C" void
 openmc_set_seed(int64_t new_seed)
 {
   seed = new_seed;
-#pragma omp parallel
+  #pragma omp parallel
   {
     for (int i = 0; i < N_STREAMS; i++) {
       prn_seed[i] = seed + i;

src/settings.cpp

@@ -383,20 +383,8 @@ void read_settings_xml()
 
   // Number of OpenMP threads
   if (check_for_node(root, "threads")) {
-#ifdef _OPENMP
-    if (simulation::n_threads == 0) {
-      simulation::n_threads = std::stoi(get_node_value(root, "threads"));
-      if (simulation::n_threads < 1) {
-        std::stringstream msg;
-        msg << "Invalid number of threads: " << simulation::n_threads;
-        fatal_error(msg);
-      }
-      omp_set_num_threads(simulation::n_threads);
-    }
-#else
-    if (mpi::master) warning("OpenMC was not compiled with OpenMP support; "
-      "ignoring number of threads.");
-#endif
+    if (mpi::master) warning("The <threads> element has been deprecated. Use "
+      "the OMP_NUM_THREADS environment variable to set the number of threads.");
   }
 
   // ==========================================================================

src/simulation.cpp

@@ -20,7 +20,9 @@
 #include "openmc/tallies/tally.h"
 #include "openmc/tallies/trigger.h"
 
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 #include "xtensor/xview.hpp"
 
 #include <algorithm>
@@ -59,7 +61,7 @@ int openmc_simulation_init()
   calculate_work();
 
   // Allocate array for matching filter bins
-#pragma omp parallel
+  #pragma omp parallel
   {
     simulation::filter_matches.resize(model::tally_filters.size());
   }
@@ -136,7 +138,7 @@ int openmc_simulation_finalize()
   // Write tally results to tallies.out
   if (settings::output_tallies && mpi::master) write_tallies();
 
-#pragma omp parallel
+  #pragma omp parallel
   {
     simulation::filter_matches.clear();
   }
@@ -186,7 +188,7 @@ int openmc_next_batch(int* status)
     // ====================================================================
     // LOOP OVER PARTICLES
 
-#pragma omp parallel for schedule(runtime)
+    #pragma omp parallel for schedule(runtime)
     for (int64_t i_work = 1; i_work <= simulation::work; ++i_work) {
       simulation::current_work = i_work;
 
@@ -250,10 +252,6 @@ std::vector<int64_t> work_index;
 
 // Threadprivate variables
 bool trace;     //!< flag to show debug information
-#ifdef _OPENMP
-int n_threads {-1};  //!< number of OpenMP threads
-int thread_id;  //!< ID of a given thread
-#endif
 
 } // namespace simulation
 
@@ -273,15 +271,13 @@ void allocate_banks()
     // a generation, there is also a 'master_fission_bank' that is used to
     // collect the sites from each thread.
 
-    simulation::n_threads = omp_get_max_threads();
-
-#pragma omp parallel
+    #pragma omp parallel
     {
-      simulation::thread_id = omp_get_thread_num();
-      if (simulation::thread_id == 0) {
+      if (omp_get_thread_num() == 0) {
         simulation::fission_bank.reserve(3*simulation::work);
       } else {
-        simulation::fission_bank.reserve(3*simulation::work / simulation::n_threads);
+        int n_threads = omp_get_num_threads();
+        simulation::fission_bank.reserve(3*simulation::work / n_threads);
       }
     }
     simulation::master_fission_bank.reserve(3*simulation::work);
@@ -403,9 +399,9 @@ void finalize_generation()
   auto& gt = simulation::global_tallies;
 
   // Update global tallies with the omp private accumulation variables
-#pragma omp parallel
+  #pragma omp parallel
   {
-#pragma omp critical(increment_global_tallies)
+    #pragma omp critical(increment_global_tallies)
     {
       if (settings::run_mode == RUN_MODE_EIGENVALUE) {
         gt(K_COLLISION, RESULT_VALUE) += global_tally_collision;

tests/unit_tests/test_settings.py

@@ -36,7 +36,6 @@ def test_export_to_xml(run_in_tmpdir):
     s.tabular_legendre = {'enable': True, 'num_points': 50}
     s.temperature = {'default': 293.6, 'method': 'interpolation',
                      'multipole': True, 'range': (200., 1000.)}
-    s.threads = 8
     s.trace = (10, 1, 20)
     s.track = [1, 1, 1, 2, 1, 1]
     s.ufs_mesh = mesh