IM-1787: Improve memory efficiency of threshold plugin

doc/source/Code-Style-Guide.rst

@@ -342,7 +342,7 @@ Plugins (classes) should be an example of a non-trivial algorithm or set
 of algorithms for a particular purpose. They should be set up via the
 ``__init__`` method and then invoked on a particular iris Cube ``cube``
 using a ``process`` method - e.g. using ``process(cube)``. See
-e.g. `BasicThreshold <https://github.com/metoppv/improver/blob/master/lib/improver/threshold.py>`_
+e.g. `Threshold <https://github.com/metoppv/improver/blob/master/lib/improver/threshold.py>`_
 class. In some limited cases an iris ``CubeList`` may be preferable.
 Avoid writing code that can do both. Class names use
 `PascalCase <https://en.wikipedia.org/wiki/PascalCase>`_ whilst

improver/cli/threshold.py

@@ -58,6 +58,10 @@ def process(
     Args:
         cube (iris.cube.Cube):
             A cube to be processed.
+        land_sea_mask (Cube):
+            Binary land-sea mask data. True for land-points, False for sea.
+            Restricts in-vicinity processing to only include points of a
+            like mask value.
         threshold_values (list of float):
             Threshold value or values about which to calculate the truth
             values; e.g. 270,300. Must be omitted if 'threshold_config'
@@ -104,10 +108,6 @@ def process(
             List of distances in metres used to define the vicinities within
             which to search for an occurrence. Each vicinity provided will
             lead to a different gridded field.
-        land_sea_mask (Cube):
-            Binary land-sea mask data. True for land-points, False for sea.
-            Restricts in-vicinity processing to only include points of a
-            like mask value.
         fill_masked (float):
             If provided all masked points in cube will be replaced with the
             provided value before thresholding.
@@ -119,16 +119,8 @@ def process(
     Raises:
         ValueError: If threshold_config and threshold_values are both set
         ValueError: If threshold_config is used for fuzzy thresholding
-        ValueError: Cannot apply land-mask cube without in-vicinity processing.
-        ValueError: Can only collapse over a realization coordinate or a percentile
-            coordinate that has been rebadged as a realization coordinate.
     """
-    from improver.ensemble_copula_coupling.ensemble_copula_coupling import (
-        RebadgePercentilesAsRealizations,
-    )
-    from improver.threshold import BasicThreshold
-    from improver.utilities.cube_manipulation import collapse_realizations
-    from improver.utilities.spatial import OccurrenceWithinVicinity
+    from improver.threshold import Threshold
 
     if threshold_config and threshold_values:
         raise ValueError(
@@ -137,56 +129,16 @@ def process(
         )
     if threshold_config and fuzzy_factor:
         raise ValueError("--threshold-config cannot be used for fuzzy thresholding")
-    if threshold_config:
-        thresholds = []
-        fuzzy_bounds = []
-        for key in threshold_config.keys():
-            # Ensure thresholds are float64 to avoid rounding errors during
-            # possible unit conversion.
-            thresholds.append(float(key))
-            # If the first threshold has no bounds, fuzzy_bounds is
-            # set to None and subsequent bounds checks are skipped
-            if threshold_config[key] == "None":
-                fuzzy_bounds = None
-                continue
-            fuzzy_bounds.append(tuple(threshold_config[key]))
-    else:
-        # Ensure thresholds are float64 to avoid rounding errors during possible
-        # unit conversion.
-        thresholds = [float(x) for x in threshold_values]
-        fuzzy_bounds = None
-
-    each_threshold_func_list = []
-
-    if vicinity is not None:
-        vicinity = [float(x) for x in vicinity]
-        # smooth thresholded occurrences over local vicinity
-        each_threshold_func_list.append(
-            OccurrenceWithinVicinity(radii=vicinity, land_mask_cube=land_sea_mask)
-        )
-    elif land_sea_mask:
-        raise ValueError("Cannot apply land-mask cube without in-vicinity processing")
-
-    if collapse_coord == "realization":
-        each_threshold_func_list.append(collapse_realizations)
-    elif collapse_coord == "percentile":
-        cube = RebadgePercentilesAsRealizations()(cube)
-        each_threshold_func_list.append(collapse_realizations)
-    elif collapse_coord is not None:
-        raise ValueError(
-            "Can only collapse over a realization coordinate or a percentile "
-            "coordinate that has been rebadged as a realization coordinate."
-        )
-
     if fill_masked is not None:
         fill_masked = float(fill_masked)
 
-    return BasicThreshold(
-        thresholds,
+    return Threshold(
+        threshold_values=threshold_values,
+        threshold_config=threshold_config,
         fuzzy_factor=fuzzy_factor,
-        fuzzy_bounds=fuzzy_bounds,
         threshold_units=threshold_units,
         comparison_operator=comparison_operator,
-        each_threshold_func=each_threshold_func_list,
+        collapse_coord=collapse_coord,
+        vicinity=vicinity,
         fill_masked=fill_masked,
-    )(cube)
+    )(cube, land_sea_mask)

improver/precipitation_type/shower_condition_probability.py

@@ -44,7 +44,7 @@
     create_new_diagnostic_cube,
     generate_mandatory_attributes,
 )
-from improver.threshold import BasicThreshold
+from improver.threshold import Threshold
 from improver.utilities.cube_manipulation import collapse_realizations
 
 from .utilities import make_shower_condition_cube
@@ -171,10 +171,10 @@ def process(self, cubes: CubeList) -> Cube:
         cloud, convection = self._extract_inputs(cubes)
 
         # Threshold cubes
-        cloud_thresholded = BasicThreshold(
+        cloud_thresholded = Threshold(
             self.cloud_threshold, comparison_operator="<="
         ).process(cloud)
-        convection_thresholded = BasicThreshold(self.convection_threshold).process(
+        convection_thresholded = Threshold(self.convection_threshold).process(
             convection
         )
 

improver/regrid/landsea.py

@@ -45,7 +45,7 @@
 from improver.metadata.constants.attributes import MANDATORY_ATTRIBUTE_DEFAULTS
 from improver.metadata.constants.mo_attributes import MOSG_GRID_ATTRIBUTES
 from improver.regrid.landsea2 import RegridWithLandSeaMask
-from improver.threshold import BasicThreshold
+from improver.threshold import Threshold
 from improver.utilities.cube_checker import spatial_coords_match
 from improver.utilities.spatial import OccurrenceWithinVicinity
 
@@ -288,9 +288,9 @@ def _get_matches(
         # Identify nearby points on regridded input_land that match the
         # selector_value
         if selector_val > 0.5:
-            thresholder = BasicThreshold(0.5)
+            thresholder = Threshold(0.5)
         else:
-            thresholder = BasicThreshold(0.5, comparison_operator="<=")
+            thresholder = Threshold(0.5, comparison_operator="<=")
         in_vicinity = self.vicinity(thresholder(self.input_land))
 
         # Identify those points sourced from the opposite mask that are