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Speed up operations that use the Coord.cells method for time coordinates #4969

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Merged
trexfeathers merged 4 commits into from
Sep 29, 2022
Merged

Speed up operations that use the Coord.cells method for time coordinates #4969

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153e662
Convert all time points at once before generating cells
bouweandela Sep 16, 2022
7eafc33
Small simplification
bouweandela Sep 23, 2022
c3bd718
Add a whatnew entry
bouweandela Sep 29, 2022
aa31d47
Fix link
bouweandela Sep 29, 2022
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6 changes: 5 additions & 1 deletion docs/src/whatsnew/latest.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ This document explains the changes made to Iris for this release
#. `@bjlittle`_ and `@lbdreyer`_ (reviewer) fixed the building of the CF
Standard Names module ``iris.std_names`` for the ``setup.py`` commands
``develop`` and ``std_names``. (:issue:`4951`, :pull:`4952`)

#. `@lbdreyer`_ and `@pp-mo`_ (reviewer) fixed the cube print out such that
scalar ancillary variables are displayed in a dedicated section rather than
being added to the vector ancillary variables section. Further, ancillary
Expand All @@ -71,6 +71,10 @@ This document explains the changes made to Iris for this release
:obj:`~iris.analysis.SUM`, :obj:`~iris.analysis.COUNT` and
:obj:`~iris.analysis.PROPORTION` on real data. (:pull:`4905`)

#. `@bouweandela` made :meth:`iris.coords.Coord.cells` faster for time
coordinates. This also affects :meth:`iris.cube.Cube.extract`,
:meth:`iris.cube.Cube.subset`, and :meth:`iris.coords.Coord.intersect`.
(:pull:`4969`)

🔥 Deprecations
===============
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33 changes: 16 additions & 17 deletions lib/iris/coords.py
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Expand Up @@ -1895,7 +1895,22 @@ def cells(self):
...

"""
return _CellIterator(self)
if self.ndim != 1:
raise iris.exceptions.CoordinateMultiDimError(self)

points = self.points
bounds = self.bounds
if self.units.is_time_reference():
points = self.units.num2date(points)
if self.has_bounds():
bounds = self.units.num2date(bounds)

if self.has_bounds():
for point, bound in zip(points, bounds):
yield Cell(point, bound)
else:
for point in points:
yield Cell(point)

def _sanity_check_bounds(self):
if self.ndim == 1:
Expand Down Expand Up @@ -3137,22 +3152,6 @@ def xml_element(self, doc):
return cellMethod_xml_element


# See Coord.cells() for the description/context.
class _CellIterator(Iterator):
def __init__(self, coord):
self._coord = coord
if coord.ndim != 1:
raise iris.exceptions.CoordinateMultiDimError(coord)
self._indices = iter(range(coord.shape[0]))

def __next__(self):
# NB. When self._indices runs out it will raise StopIteration for us.
i = next(self._indices)
return self._coord.cell(i)

next = __next__


# See ExplicitCoord._group() for the description/context.
class _GroupIterator(Iterator):
def __init__(self, points):
Expand Down