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Speedup area weighted regridding #2730

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Merged
pelson merged 4 commits into from
Oct 24, 2017
Merged

Speedup area weighted regridding #2730

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c4a4325
Use faster np.average if nothing is masked.
tv3141 May 18, 2017
3c4cb5a
Get weights sum from ma.average.
tv3141 May 18, 2017
2cd91f9
Add old function for comparison.
tv3141 Aug 4, 2017
a1b485e
Remove old function used for comparison.
tv3141 Oct 11, 2017
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32 changes: 16 additions & 16 deletions lib/iris/experimental/regrid.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,6 @@
Regridding functions.

"""

from __future__ import (absolute_import, division, print_function)
from six.moves import (filter, input, map, range, zip) # noqa
import six
Expand Down Expand Up @@ -384,21 +383,22 @@ def _weighted_mean_with_mdtol(data, weights, axis=None, mdtol=0):
Numpy array (possibly masked) or scalar.

"""
res = ma.average(data, weights=weights, axis=axis)
if ma.isMaskedArray(data) and mdtol < 1:
weights_total = weights.sum(axis=axis)
masked_weights = weights.copy()
masked_weights[~ma.getmaskarray(data)] = 0
masked_weights_total = masked_weights.sum(axis=axis)
frac_masked = np.true_divide(masked_weights_total, weights_total)
mask_pt = frac_masked > mdtol
if np.any(mask_pt):
if np.isscalar(res):
res = ma.masked
elif ma.isMaskedArray(res):
res.mask |= mask_pt
else:
res = ma.masked_array(res, mask=mask_pt)
if ma.is_masked(data):
res, unmasked_weights_sum = ma.average(data, weights=weights,
axis=axis, returned=True)
if mdtol < 1:
weights_sum = weights.sum(axis=axis)
frac_masked = 1 - np.true_divide(unmasked_weights_sum, weights_sum)
mask_pt = frac_masked > mdtol
if np.any(mask_pt):
if np.isscalar(res):
res = ma.masked
elif ma.isMaskedArray(res):
res.mask |= mask_pt
else:
res = ma.masked_array(res, mask=mask_pt)
else:
res = np.average(data, weights=weights, axis=axis)
return res


Expand Down