Add test checking that collision/tracklength estimators agree for sph/cyl mesh

tests/unit_tests/test_filter_mesh.py

@@ -0,0 +1,109 @@
+import numpy as np
+import openmc
+from uncertainties import unumpy
+
+
+def test_spherical_mesh_estimators(run_in_tmpdir):
+    """Test that collision/tracklength estimators agree for SphericalMesh"""
+
+    mat = openmc.Material()
+    mat.add_nuclide('U235', 1.0)
+    mat.set_density('g/cm3', 10.0)
+
+    sphere = openmc.Sphere(r=10.0, boundary_type='vacuum')
+    cell = openmc.Cell(fill=mat, region=-sphere)
+    model = openmc.Model()
+    model.geometry = openmc.Geometry([cell])
+    model.settings.particles = 1_000
+    model.settings.inactive = 10
+    model.settings.batches = 20
+
+    sph_mesh = openmc.SphericalMesh()
+    sph_mesh.r_grid = np.linspace(0.0, 5.0**3, 20)**(1/3)
+    tally1 = openmc.Tally()
+    tally1.filters = [openmc.MeshFilter(sph_mesh)]
+    tally1.scores = ['flux']
+    tally1.estimator = 'collision'
+
+    sph_mesh = openmc.SphericalMesh()
+    sph_mesh.r_grid = np.linspace(0.0, 5.0**3, 20)**(1/3)
+    tally2 = openmc.Tally()
+    tally2.filters = [openmc.MeshFilter(sph_mesh)]
+    tally2.scores = ['flux']
+    tally2.estimator = 'tracklength'
+
+    model.tallies = openmc.Tallies([tally1, tally2])
+
+    # Run OpenMC
+    sp_filename = model.run()
+
+    # Get radial flux distribution
+    with openmc.StatePoint(sp_filename) as sp:
+        flux_collision = sp.tallies[tally1.id].mean.ravel()
+        flux_collision_unc = sp.tallies[tally1.id].std_dev.ravel()
+        flux_tracklength = sp.tallies[tally2.id].mean.ravel()
+        flux_tracklength_unc = sp.tallies[tally2.id].std_dev.ravel()
+
+    # Construct arrays with uncertainties
+    collision = unumpy.uarray(flux_collision, flux_collision_unc)
+    tracklength = unumpy.uarray(flux_tracklength, flux_tracklength_unc)
+    delta = collision - tracklength
+
+    # Check that difference is within uncertainty
+    diff = unumpy.nominal_values(delta)
+    std_dev = unumpy.std_devs(delta)
+    assert np.all(diff < 3*std_dev)
+
+
+def test_cylindrical_mesh_estimators(run_in_tmpdir):
+    """Test that collision/tracklength estimators agree for CylindricalMesh"""
+
+    mat = openmc.Material()
+    mat.add_nuclide('U235', 1.0)
+    mat.set_density('g/cm3', 10.0)
+
+    cyl = openmc.model.RightCircularCylinder((0., 0., -5.), 10., 10.0, boundary_type='vacuum')
+    cell = openmc.Cell(fill=mat, region=-cyl)
+    model = openmc.Model()
+    model.geometry = openmc.Geometry([cell])
+    model.settings.particles = 1_000
+    model.settings.inactive = 10
+    model.settings.batches = 20
+
+    cyl_mesh = openmc.CylindricalMesh()
+    cyl_mesh.r_grid = np.linspace(0.0, 5.0**3, 20)**(1/3)
+    cyl_mesh.z_grid = [-5., 5.]
+    tally1 = openmc.Tally()
+    tally1.filters = [openmc.MeshFilter(cyl_mesh)]
+    tally1.scores = ['flux']
+    tally1.estimator = 'collision'
+
+    cyl_mesh = openmc.CylindricalMesh()
+    cyl_mesh.r_grid = np.linspace(0.0, 5.0**3, 20)**(1/3)
+    cyl_mesh.z_grid = [-5., 5.]
+    tally2 = openmc.Tally()
+    tally2.filters = [openmc.MeshFilter(cyl_mesh)]
+    tally2.scores = ['flux']
+    tally2.estimator = 'tracklength'
+
+    model.tallies = openmc.Tallies([tally1, tally2])
+
+    # Run OpenMC
+    sp_filename = model.run()
+
+    # Get radial flux distribution
+    with openmc.StatePoint(sp_filename) as sp:
+        flux_collision = sp.tallies[tally1.id].mean.ravel()
+        flux_collision_unc = sp.tallies[tally1.id].std_dev.ravel()
+        flux_tracklength = sp.tallies[tally2.id].mean.ravel()
+        flux_tracklength_unc = sp.tallies[tally2.id].std_dev.ravel()
+
+    # Construct arrays with uncertainties
+    collision = unumpy.uarray(flux_collision, flux_collision_unc)
+    tracklength = unumpy.uarray(flux_tracklength, flux_tracklength_unc)
+    delta = collision - tracklength
+
+    # Check that difference is within uncertainty
+    diff = unumpy.nominal_values(delta)
+    std_dev = unumpy.std_devs(delta)
+    assert np.all(diff < 3*std_dev)