Optimize depletion chain loading and material activity calculations

openmc/_xml.py

@@ -1,3 +1,6 @@
+import numpy as np
+
+
 def clean_indentation(element, level=0, spaces_per_level=2, trailing_indent=True):
     """Set indentation of XML element and its sub-elements.
     Copied and pasted from https://effbot.org/zone/element-lib.htm#prettyprint.
@@ -84,3 +87,28 @@ def get_elem_list(elem, name, dtype=int):
     text = get_text(elem, name)
     if text is not None:
         return [dtype(x) for x in text.split()]
+
+
+def get_elem_array(elem, name, dtype=int):
+    """Helper function to get an array of values from an elem
+
+    Parameters
+    ----------
+    elem : lxml.etree._Element
+        XML element that should contain a tuple
+    name : str
+        Name of the subelement to obtain tuple from
+    dtype : data-type
+        The type of each element in the tuple
+
+    Returns
+    -------
+    numpy.ndarray
+        Data read from the list
+    """
+    text = get_text(elem, name)
+    if text is not None:
+        text = text.strip()
+        if not text:
+            return np.array([], dtype=dtype)
+        return np.fromstring(text, sep=' ', dtype=dtype)

openmc/data/decay.py

@@ -513,11 +513,9 @@ def sources(self):
                 'neutrino': 'neutrino',
             }[particle]
 
-            if particle_type not in sources:
-                sources[particle_type] = []
-
             # Create distribution for discrete
-            if spectra['continuous_flag'] in ('discrete', 'both'):
+            if (spectra['continuous_flag'] in ('discrete', 'both')
+                    and spectra['discrete']):
                 energies = []
                 intensities = []
                 for discrete_data in spectra['discrete']:
@@ -527,7 +525,7 @@ def sources(self):
                 intensity = spectra['discrete_normalization'].n
                 rates = decay_constant * intensity * np.array(intensities)
                 dist_discrete = Discrete(energies, rates)
-                sources[particle_type].append(dist_discrete)
+                sources.setdefault(particle_type, []).append(dist_discrete)
 
             # Create distribution for continuous
             if spectra['continuous_flag'] in ('continuous', 'both'):
@@ -543,7 +541,7 @@ def sources(self):
                 intensity = spectra['continuous_normalization'].n
                 rates = decay_constant * intensity * f.y
                 dist_continuous = Tabular(f.x, rates, interpolation)
-                sources[particle_type].append(dist_continuous)
+                sources.setdefault(particle_type, []).append(dist_continuous)
 
         # Combine discrete distributions
         merged_sources = {}

openmc/deplete/chain.py

@@ -563,9 +563,6 @@ def from_xml(cls, filename, fission_q=None):
             nuc = Nuclide.from_xml(nuclide_elem, root, this_q)
             chain.add_nuclide(nuc)
 
-        # Store path of XML file (used for handling cache invalidation)
-        chain._xml_path = str(Path(filename).resolve())
-
         return chain
 
     def export_to_xml(self, filename):
@@ -1408,12 +1405,18 @@ def _get_chain(
     elif not isinstance(chain_file, PathLike):
         raise TypeError("chain_file must be path-like, a Chain, or None")
 
-    # Determine the key for the cache, which consists of the absolute path, the
-    # file modification time, the file size, and the fission Q values.
-    chain_path = Path(chain_file).resolve()
+    # Determine the key for the cache, which consists of the file identity,
+    # modification time, file size, and fission Q values.
+    chain_path = Path(chain_file).absolute()
     stat_result = chain_path.stat()
     fq_tuple = tuple(sorted(fission_q.items())) if fission_q else ()
-    key = (chain_path, stat_result.st_mtime, stat_result.st_size, fq_tuple)
+    key = (
+        stat_result.st_dev,
+        stat_result.st_ino,
+        stat_result.st_mtime_ns,
+        stat_result.st_size,
+        fq_tuple,
+    )
 
     # Check the global cache. If not cached, load the chain from XML and store
     global _CHAIN_CACHE
@@ -1423,10 +1426,8 @@ def _get_chain(
 
 
 def _invalidate_chain_cache(chain):
-    """Invalidate the cache for a specific Chain (when it is modifed)."""
+    """Invalidate the cache for a specific Chain (when it is modified)."""
     chain._decay_matrix = None
-    if hasattr(chain, '_xml_path'):
-        # Remove all entries with the same path as self._xml_path
-        for key in list(_CHAIN_CACHE.keys()):
-            if str(key[0]) == chain._xml_path:
-                del _CHAIN_CACHE[key]
+    for key, cached_chain in list(_CHAIN_CACHE.items()):
+        if cached_chain is chain:
+            del _CHAIN_CACHE[key]

openmc/deplete/nuclide.py

@@ -245,6 +245,11 @@ def from_xml(cls, element, root=None, fission_q=None):
 
         # Check for sources
         for src_elem in element.iter('source'):
+            # Skip source elements with empty parameters
+            parameters = src_elem.find('parameters')
+            if parameters is not None and not (parameters.text or '').strip():
+                continue
+
             particle = get_text(src_elem, "particle")
             distribution = Univariate.from_xml_element(src_elem)
             nuc.sources[particle] = distribution

openmc/material.py

@@ -1455,10 +1455,15 @@ def get_activity(
         elif units == 'Ci/m3':
             multiplier = 1e6 / _BECQUEREL_PER_CURIE
 
+        # Resolve chain to avoid repeated lookups for each nuclide
+        from openmc.deplete.chain import _get_chain
+        if chain_file is not False:
+            if chain_file is not None or openmc.config.get('chain_file') is not None:
+                chain_file = _get_chain(chain_file)
+
         activity = {}
         for nuclide, atoms_per_bcm in self.get_nuclide_atom_densities().items():
-            inv_seconds = openmc.data.decay_constant(
-                nuclide, chain_file=chain_file)
+            inv_seconds = openmc.data.decay_constant(nuclide, chain_file=chain_file)
             activity[nuclide] = inv_seconds * 1e24 * atoms_per_bcm * multiplier
 
         return activity if by_nuclide else sum(activity.values())

openmc/stats/univariate.py

@@ -17,7 +17,7 @@
 import openmc.checkvalue as cv
 from openmc.data import atomic_mass, NEUTRON_MASS
 import openmc.data
-from .._xml import get_elem_list, get_text
+from .._xml import get_elem_list, get_text, get_elem_array
 from ..mixin import EqualityMixin
 
 _INTERPOLATION_SCHEMES = {
@@ -403,7 +403,7 @@ def from_xml_element(cls, elem: ET.Element):
             Discrete distribution generated from XML element
 
         """
-        params = get_elem_list(elem, "parameters", float)
+        params = get_elem_array(elem, "parameters", float)
         x = params[:len(params)//2]
         p = params[len(params)//2:]
         bias_dist = cls._read_array_bias_from_xml(elem)
@@ -1768,7 +1768,7 @@ def from_xml_element(cls, elem: ET.Element):
 
         """
         interpolation = get_text(elem, 'interpolation')
-        params = get_elem_list(elem, "parameters", float)
+        params = get_elem_array(elem, "parameters", float)
         m = (len(params) + 1)//2  # +1 for when len(params) is odd
         x = params[:m]
         p = params[m:]

tests/unit_tests/test_deplete_chain.py

@@ -90,6 +90,24 @@ def test_unstable_nuclides(simple_chain: Chain):
     assert [nuc.name for nuc in simple_chain.unstable_nuclides] == ["A", "B"]
 
 
+def test_from_xml_empty_source(tmp_path):
+    """Ignore legacy chain sources with no distribution parameters."""
+    chain_path = tmp_path / 'chain.xml'
+    chain_path.write_text("""\
+<depletion_chain>
+  <nuclide name="Sm164" half_life="1.226" decay_modes="0"
+    decay_energy="0.0" reactions="0">
+    <source type="discrete" particle="neutron">
+      <parameters> </parameters>
+    </source>
+  </nuclide>
+</depletion_chain>
+""")
+
+    chain = Chain.from_xml(chain_path)
+    assert chain['Sm164'].sources == {}
+
+
 def test_stable_nuclides(simple_chain: Chain):
     assert [nuc.name for nuc in simple_chain.stable_nuclides] == ["H1", "C"]