Steal the algorithm used to combine hashes from tupleobject.c #15227
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Here's an initial pass at stealing https://github.com/python-git/python/blob/master/Objects/tupleobject.c#L290 for the combining. I am not 100% that the problem is my (rather crude) combiner, but possibly the exact way we're using the bitmixer in hash_array. I'm trying to think about it........I think we might be maintaining undesirable linearity. May I ask, how did you encounter these collisions? |
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If the basic approach looks sound I can add some comments around some of the lazy iterator wackiness. |
jreback
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Jan 25, 2017
| arrays = itertools.chain([first], arrays) | ||
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| mult = np.zeros_like(first) + np.uint64(1000003) | ||
| out = np.zeros_like(first) + np.uint64(0x345678L) |
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the L is not working in py3. (remove it and its ok).
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@mikegraham the collisions I found by hashing which is basically a cartesian product of 1000 x 1000. nothing special really, just a test case I am using. |
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closing in favor of in #15224 thanks @mikegraham |
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Jan 27, 2017
closes #15227 Author: Jeff Reback <[email protected]> Author: Mike Graham <mikegraham2gmail.com> Closes #15224 from jreback/mi_hash2 and squashes the following commits: 8b1d3f9 [Jeff Reback] not correctly hashing categorical in a MI 48a2402 [Jeff Reback] support for mixed type arrays 58f682d [Jeff Reback] memory optimization 0c13df7 [Mike Graham] Steal the algorithm used to combine hashes from tupleobject.c e8dd607 [Jeff Reback] add hash_tuples 44e9c7d [Mike Graham] wipSteal the algorithm used to combine hashes from tupleobject.c e507c4a [Jeff Reback] ENH: support MultiIndex and tuple hashing
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Mar 21, 2017
closes pandas-dev#15227 Author: Jeff Reback <[email protected]> Author: Mike Graham <mikegraham2gmail.com> Closes pandas-dev#15224 from jreback/mi_hash2 and squashes the following commits: 8b1d3f9 [Jeff Reback] not correctly hashing categorical in a MI 48a2402 [Jeff Reback] support for mixed type arrays 58f682d [Jeff Reback] memory optimization 0c13df7 [Mike Graham] Steal the algorithm used to combine hashes from tupleobject.c e8dd607 [Jeff Reback] add hash_tuples 44e9c7d [Mike Graham] wipSteal the algorithm used to combine hashes from tupleobject.c e507c4a [Jeff Reback] ENH: support MultiIndex and tuple hashing
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closes #15224