Fix symmetrical case for hellinger distance. Fix #1854 #1860
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This changes fix the bugs that return different distance when we call hellinger(x, y) and hellinger(y, x). The cause of this bug is that we compute the distance based on one distribution's index previously, but we should iterate all the index appears in two probability distributions.
menshikh-iv
suggested changes
Jan 26, 2018
gensim/matutils.py
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| @@ -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()) | |||
gensim/matutils.py
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| 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
menshikh-iv
changed the title
* fix the currrent test for different length BOW inputs * add a test for symmetrical inputs
|
Good work @caiyulun, congratz with first contribution 👍 |
sj29-innovate
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Feb 21, 2018
…vorky#1860) * fix: fix bugs in hellinger distance computing This changes fix the bugs that return different distance when we call hellinger(x, y) and hellinger(y, x). The cause of this bug is that we compute the distance based on one distribution's index previously, but we should iterate all the index appears in two probability distributions. * rename variable + fix union indices error in python3 * fix and add tests for hellinger distance * fix the currrent test for different length BOW inputs * add a test for symmetrical inputs
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This changes fix the bugs that return different distance when we call hellinger(x, y) and hellinger(y,x) ( #1854)
The cause of this bug is that we compute the distance based on one distribution's index previously, but we should iterate all the index appears in two probability distributions.