Added unit cache in front of pint registry.

common/python/nomadcore/unit_conversion/unit_conversion.py

@@ -15,7 +15,18 @@ from pint import UnitRegistry
 logger = logging.getLogger(__name__)
 # disable warnings from pint
 logging.getLogger("pint").setLevel(logging.ERROR)
+
 ureg = UnitRegistry(os.path.join(os.path.dirname(__file__), "units.txt"))
+_ureg_cache = dict()
+
+
+def ureg_cached(unit):
+    if unit in _ureg_cache:
+        return _ureg_cache[unit]
+    else:
+        unit_def = ureg(unit)
+        _ureg_cache[unit] = unit_def
+        return unit_def
 
 
 #===============================================================================
@@ -51,7 +62,7 @@ def convert_unit(value, unit, target_unit=None):
     """
 
     # Check that the unit is valid
-    unit_def = ureg(unit)
+    unit_def = ureg_cached(unit)
     if not unit_def:
         logger.error("Undefined unit given. Cannot do the conversion")
         return
@@ -64,7 +75,7 @@ def convert_unit(value, unit, target_unit=None):
         return converted_value.magnitude
     else:
         # Check that the given target unit is valid
-        target_unit_def = ureg(target_unit)
+        target_unit_def = ureg_cached(target_unit)
         if not target_unit_def:
             logger.error("Undefined target unit given. Cannot do the conversion")
             return
@@ -95,9 +106,9 @@ def convert_unit_function_immediate(unit, target_unit=None):
     """
     # Check that the dimensionality of the source and target units match.
     if target_unit is not None:
-        source = ureg(target_unit)
+        source = ureg_cached(target_unit)
         source_dim = source.dimensionality
-        target = ureg(unit)
+        target = ureg_cached(unit)
         target_dim = target.dimensionality
         if source_dim != target_dim:
             raise Exception("The dimensionality of unit '{}' does not match the dimensionality of unit '{}'. Cannot do the unit conversion.".format(unit, target_unit))