Add regression test for new DAGUniverse constructor

tests/regression_tests/dagmc/external/dagmc.h5m

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+../legacy/dagmc.h5m

tests/regression_tests/dagmc/external/inputs_true.dat

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+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <dagmc_universe filename="dagmc.h5m" id="1" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="40" name="no-void fuel">
+    <density units="g/cc" value="11" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="41" name="water">
+    <density units="g/cc" value="1.0" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+    <sab name="c_H_in_H2O" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>eigenvalue</run_mode>
+  <particles>100</particles>
+  <batches>5</batches>
+  <inactive>0</inactive>
+  <source strength="1.0">
+    <space type="box">
+      <parameters>-4 -4 -4 4 4 4</parameters>
+    </space>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <filter id="1" type="cell">
+    <bins>1</bins>
+  </filter>
+  <tally id="1">
+    <filters>1</filters>
+    <scores>total</scores>
+  </tally>
+</tallies>

tests/regression_tests/dagmc/external/main.cpp

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+#include "openmc/capi.h"
+#include "openmc/cross_sections.h"
+#include "openmc/dagmc.h"
+#include "openmc/error.h"
+#include "openmc/geometry.h"
+#include "openmc/geometry_aux.h"
+#include "openmc/nuclide.h"
+#include <iostream>
+
+int main(int argc, char* argv[])
+{
+  using namespace openmc;
+  int openmc_err;
+
+  // Initialise OpenMC
+  openmc_err = openmc_init(argc, argv, nullptr);
+  if (openmc_err == -1) {
+    // This happens for the -h and -v flags
+    return EXIT_SUCCESS;
+  } else if (openmc_err) {
+    fatal_error(openmc_err_msg);
+  }
+
+  // Create DAGMC ptr
+  std::string filename = "dagmc.h5m";
+  std::shared_ptr<moab::DagMC> dag_ptr = std::make_shared<moab::DagMC>();
+  moab::ErrorCode rval = dag_ptr->load_file(filename.c_str());
+  if (rval != moab::MB_SUCCESS) {
+    fatal_error("Failed to load file");
+  }
+
+  // Initialize acceleration data structures
+  rval = dag_ptr->init_OBBTree();
+  if (rval != moab::MB_SUCCESS) {
+    fatal_error("Failed to initialise OBB tree");
+  }
+
+  // Get rid of existing geometry
+  std::unordered_map<std::string, int> nuclide_map_copy =
+    openmc::data::nuclide_map;
+  openmc::data::nuclides.clear();
+  openmc::data::nuclide_map = nuclide_map_copy;
+  openmc::model::surfaces.clear();
+  openmc::model::surface_map.clear();
+  openmc::model::cells.clear();
+  openmc::model::cell_map.clear();
+  openmc::model::universes.clear();
+  openmc::model::universe_map.clear();
+
+  // Create new DAGMC universe
+  openmc::model::universes.push_back(
+    std::make_unique<openmc::DAGUniverse>(dag_ptr, ""));
+  model::universe_map[model::universes.back()->id_] =
+    model::universes.size() - 1;
+
+  // Add cells to universes
+  openmc::populate_universes();
+
+  // Set root universe
+  openmc::model::root_universe = openmc::find_root_universe();
+  openmc::check_dagmc_root_univ();
+
+  // Final geometry setup and assign temperatures
+  openmc::finalize_geometry();
+
+  // Finalize cross sections having assigned temperatures
+  openmc::finalize_cross_sections();
+
+  // Run OpenMC
+  openmc_err = openmc_run();
+  if (openmc_err)
+    fatal_error(openmc_err_msg);
+
+  // Deallocate memory
+  openmc_err = openmc_finalize();
+  if (openmc_err)
+    fatal_error(openmc_err_msg);
+
+  return EXIT_SUCCESS;
+}

tests/regression_tests/dagmc/external/results_true.dat

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+k-combined:
+8.426936E-01 5.715847E-02
+tally 1:
+8.093843E+00
+1.328829E+01

tests/regression_tests/dagmc/external/test.py

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+from pathlib import Path
+import os
+import shutil
+import subprocess
+from subprocess import CalledProcessError
+import textwrap
+import glob
+from itertools import product
+
+import openmc
+import openmc.lib
+import numpy as np
+import pytest
+
+from tests.regression_tests import config
+from tests.testing_harness import PyAPITestHarness
+
+pytestmark = pytest.mark.skipif(
+    not openmc.lib._dagmc_enabled(),
+    reason="DAGMC is not enabled.")
+
+TETS_PER_VOXEL = 12
+
+# Test that an external DAGMC instance can be passed in through the C API
+
+@pytest.fixture
+def cpp_driver(request):
+    """Compile the external source"""
+
+    # Get build directory and write CMakeLists.txt file
+    openmc_dir = Path(str(request.config.rootdir)) / 'build'
+    with open('CMakeLists.txt', 'w') as f:
+        f.write(textwrap.dedent("""
+            cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
+            project(openmc_cpp_driver CXX)
+            add_executable(main main.cpp)
+            find_package(OpenMC REQUIRED HINTS {})
+            target_link_libraries(main OpenMC::libopenmc)
+            set_target_properties(main PROPERTIES CXX_STANDARD
+            14 CXX_STANDARD_REQUIRED YES CXX_EXTENSIONS NO)
+            set(CMAKE_CXX_FLAGS "-pedantic-errors")
+            add_compile_definitions(DAGMC=1)
+            """.format(openmc_dir)))
+
+    # Create temporary build directory and change to there
+    local_builddir = Path('build')
+    local_builddir.mkdir(exist_ok=True)
+    os.chdir(str(local_builddir))
+
+    if config['mpi']:
+        os.environ['CXX'] = 'mpicxx'
+
+    try:
+        print("Building driver")
+        # Run cmake/make to build the shared libary
+        subprocess.run(['cmake', os.path.pardir], check=True)
+        subprocess.run(['make'], check=True)
+        os.chdir(os.path.pardir)
+
+        yield "./build/main"
+
+    finally:
+        # Remove local build directory when test is complete
+        shutil.rmtree('build')
+        os.remove('CMakeLists.txt')
+
+@pytest.fixture    
+def model():
+    model = openmc.model.Model()
+
+    # Settings
+    model.settings.batches = 5
+    model.settings.inactive = 0
+    model.settings.particles = 100
+    source_box = openmc.stats.Box([-4, -4, -4],
+                                  [ 4,  4,  4])
+    source = openmc.Source(space=source_box)
+    model.settings.source = source
+    #model.settings.dagmc = True
+
+    # Geometry
+    dag_univ = openmc.DAGMCUniverse("dagmc.h5m")
+    model.geometry = openmc.Geometry(dag_univ)
+
+    # Tallies
+    tally = openmc.Tally()
+    tally.scores = ['total']
+    tally.filters = [openmc.CellFilter(1)]
+    model.tallies = [tally]
+
+    # Materials
+    u235 = openmc.Material(name="no-void fuel")
+    u235.add_nuclide('U235', 1.0, 'ao')
+    u235.set_density('g/cc', 11)
+    u235.id = 40
+    water = openmc.Material(name="water")
+    water.add_nuclide('H1', 2.0, 'ao')
+    water.add_nuclide('O16', 1.0, 'ao')
+    water.set_density('g/cc', 1.0)
+    water.add_s_alpha_beta('c_H_in_H2O')
+    water.id = 41
+    mats = openmc.Materials([u235, water])
+    model.materials = mats
+
+    return model
+    
+class ExternalDAGMCTest(PyAPITestHarness):
+    def __init__(self, executable, statepoint_name, model):
+        super().__init__(statepoint_name, model)
+        self.executable = executable
+
+    def _run_openmc(self):
+        if config['update']:
+            # Generate the results file with internal python API
+            openmc.run(openmc_exec=config['exe'], event_based=config['event'])
+        elif config['mpi']:
+            mpi_args = [config['mpiexec'], '-n', config['mpi_np']]
+            openmc.run(openmc_exec=self.executable,
+                       mpi_args=mpi_args,
+                       event_based=config['event'])
+        else:
+            openmc.run(openmc_exec=self.executable,
+                       event_based=config['event'])
+
+def test_external_dagmc(cpp_driver, model):
+    harness = ExternalDAGMCTest(cpp_driver,'statepoint.5.h5',model)
+    harness.main()