Merge pull request neams-th-coe#853 from aprilnovak/std_dev_bug

Fix bug in tally relative error calculation.

include/base/OpenMCCellAverageProblem.h

@@ -952,7 +952,8 @@ class OpenMCCellAverageProblem : public OpenMCProblemBase
 
   /**
    * Local tallies; multiple tallies will only exist when
-   * translating multiple unstructured meshes throughout the geometry
+   * translating multiple unstructured meshes throughout the geometry. Each tally
+   * may have multiple scores which are simultaneously tracked.
    */
   std::vector<openmc::Tally *> _local_tally;
 

src/base/OpenMCCellAverageProblem.C

@@ -2886,7 +2886,8 @@ OpenMCCellAverageProblem::relaxAndNormalizeTally(const int & t, const unsigned i
   auto mean_tally = tallySum(tally, score);
   current_raw = normalizeLocalTally(mean_tally, score);
 
-  auto sum_sq = xt::view(tally->results_, xt::all(), 0, static_cast<int>(openmc::TallyResult::SUM_SQ));
+  auto sum_sq =
+      xt::view(tally->results_, xt::all(), score, static_cast<int>(openmc::TallyResult::SUM_SQ));
   auto rel_err = relativeError(mean_tally, sum_sq, tally->n_realizations_);
   current_raw_std_dev = rel_err * current_raw;
 

test/tests/postprocessors/fission_tally_relative_error/gold/ratio_out.csv

@@ -0,0 +1,3 @@
+time,heating_max,heating_min,kf_max,kf_min,max_ht,max_kf,min_ht,min_kf
+0,0,0,0,0,0,0,0,0
+1,0.035555464514196,0.029889937640975,0.035548762735905,0.029978352900852,0.035555464514196,0.035548762735905,0.029889937640975,0.029978352900852

test/tests/postprocessors/fission_tally_relative_error/ratio.i

@@ -0,0 +1,106 @@
+[Mesh]
+  [sphere]
+    type = FileMeshGenerator
+    file = ../../neutronics/meshes/sphere.e
+  []
+  [solid]
+    type = CombinerGenerator
+    inputs = sphere
+    positions = '0 0 0
+                 0 0 4
+                 0 0 8'
+  []
+[]
+
+[Problem]
+  type = OpenMCCellAverageProblem
+  power = 100.0
+  tally_blocks = '1'
+  cell_level = 0
+  tally_type = cell
+  check_tally_sum = false
+
+  tally_score = 'heating kappa_fission'
+  output = 'unrelaxed_tally_std_dev'
+  initial_properties = xml
+[]
+
+# the ratio of the std_dev variable and the output tally should give
+# the relative error in the tallies.out
+[AuxVariables]
+  [heating_rel_err]
+    family = MONOMIAL
+    order = CONSTANT
+  []
+  [kappa_fission_rel_err]
+    family = MONOMIAL
+    order = CONSTANT
+  []
+[]
+
+[AuxKernels]
+  [heating]
+    type = ParsedAux
+    variable = heating_rel_err
+    expression = 'heating_std_dev / heating'
+    coupled_variables = 'heating_std_dev heating'
+  []
+  [kappa_fission]
+    type = ParsedAux
+    variable = kappa_fission_rel_err
+    expression = 'kappa_fission_std_dev / kappa_fission'
+    coupled_variables = 'kappa_fission_std_dev kappa_fission'
+  []
+[]
+
+[Executioner]
+  type = Transient
+  num_steps = 1
+[]
+
+[Postprocessors]
+  [heating_max]
+    type = ElementExtremeValue
+    value_type = max
+    variable = heating_rel_err
+  []
+  [heating_min]
+    type = ElementExtremeValue
+    value_type = min
+    variable = heating_rel_err
+  []
+  [kf_max]
+    type = ElementExtremeValue
+    value_type = max
+    variable = kappa_fission_rel_err
+  []
+  [kf_min]
+    type = ElementExtremeValue
+    value_type = min
+    variable = kappa_fission_rel_err
+  []
+  [max_ht]
+    type = TallyRelativeError
+    value_type = max
+    tally_score = 'heating'
+  []
+  [min_ht]
+    type = TallyRelativeError
+    value_type = min
+    tally_score = 'heating'
+  []
+  [max_kf]
+    type = TallyRelativeError
+    value_type = max
+    tally_score = 'kappa_fission'
+  []
+  [min_kf]
+    type = TallyRelativeError
+    value_type = min
+    tally_score = 'kappa_fission'
+  []
+[]
+
+[Outputs]
+  csv = true
+[]

test/tests/postprocessors/fission_tally_relative_error/tests

@@ -41,4 +41,14 @@
     requirement = "The system shall error if trying to specify more than one score per postprocessor"
     required_objects = 'OpenMCCellAverageProblem'
   []
+  [manual_rel_err_calc]
+    type = CSVDiff
+    input = ratio.i
+    csvdiff = 'ratio_out.csv'
+    # This test has very few particles, and OpenMC will error if there aren't enough source particles
+    # in the fission bank on a process
+    max_parallel = 8
+    requirement = "The system shall prove equivalence between a by-hand calculation of relative error (std_dev output divided by tally value) as compared to the tally relative error postprocessor."
+    required_objects = 'OpenMCCellAverageProblem'
+  []
 []