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Fix symmetrical case for hellinger distance. Fix #1854 #1860

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merged 3 commits into from
Jan 30, 2018
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Fix symmetrical case for hellinger distance. Fix #1854 #1860

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1277067
fix: fix bugs in hellinger distance computing
caiyulun Jan 26, 2018
d4ae548
rename variable + fix union indices error in python3
caiyulun Jan 29, 2018
7ae1532
fix and add tests for hellinger distance
caiyulun Jan 29, 2018
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5 changes: 2 additions & 3 deletions gensim/matutils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -897,10 +897,9 @@ def hellinger(vec1, vec2):
if isbow(vec1) and isbow(vec2):
# if it is a BoW format, instead of converting to dense we use dictionaries to calculate appropriate distance
vec1, vec2 = dict(vec1), dict(vec2)
if len(vec2) < len(vec1):
vec1, vec2 = vec2, vec1 # swap references so that we iterate over the shorter vector
indexs = set(vec1.keys() + vec2.keys())
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indexs -> indices

sim = np.sqrt(
0.5 * sum((np.sqrt(value) - np.sqrt(vec2.get(index, 0.0)))**2 for index, value in iteritems(vec1))
0.5 * sum((np.sqrt(vec1.get(index, 0.0)) - np.sqrt(vec2.get(index, 0.0)))**2 for index in indexs)
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Also please add a test for it (you can use an example from original issue).

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Should I add a test in this function https://github.com/RaRe-Technologies/gensim/blob/develop/gensim/test/test_similarity_metrics.py#L106 or anywhere else ？ And it seems that the current two different length BOW inputs test in Line109 has a wrong expected value, I'm tring to correct it.

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Yes, please fix current test & add needed tests to TestHellinger class

)
return sim
else:
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