Issue28327
Created on 2016-10-01 12:18 by mark.dickinson, last changed 2022-04-11 14:58 by admin. This issue is now closed.
| Files | ||||
|---|---|---|---|---|
| File name | Uploaded | Description | Edit | |
| geometric_mean_int_float.patch | mark.dickinson, 2016-10-01 12:20 | review | ||
| geometric_mean_int_float_v2.patch | mark.dickinson, 2016-10-01 13:23 | review | ||
| Messages (6) | |||
|---|---|---|---|
| msg277808 - (view) | Author: Mark Dickinson (mark.dickinson) *  |
Date: 2016-10-01 12:18 | |
The following calculations should all be giving the same result:
>>> import statistics
>>> statistics.geometric_mean([2, 3, 5, 7])
3.80675409583932
>>> statistics.geometric_mean([2, 3, 5, 7.0])
1.6265765616977859
>>> statistics.geometric_mean([2, 3, 5.0, 7.0])
2.4322992790977875
>>> statistics.geometric_mean([2, 3.0, 5.0, 7.0])
3.201085872943679
>>> statistics.geometric_mean([2.0, 3.0, 5.0, 7.0])
3.80675409583932
(Correct result is 3.80675409583932.)
The culprit is this line in statistics._product:
mant, scale = 1, 0 #math.frexp(prod) # FIXME
... and indeed, we should be starting from `prod` rather than 1 here. But simply using math.frexp has potential for failure if the accumulated integer product overflows a float.
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| msg277809 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2016-10-01 12:20 | |
Here's a fix. I was planning to add tests, but as far as I can tell geometric_mean currently has no tests at all. Steve, is that correct? That seems like something that should be fixed before the 3.6 release. |
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| msg277814 - (view) | Author: Steven D'Aprano (steven.daprano) * |
Date: 2016-10-01 13:22 | |
Looks good for me. Thanks for catching this: I knew it was a bug, but then I ran into the issue that I could no longer build 3.6 before I could fix it, and between that and various issues in the real world I never got back to this. |
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| msg277815 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2016-10-01 13:23 | |
New patch, with a (very slightly) cleaner implementation of `_frexp_gen`. |
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| msg399948 - (view) | Author: Irit Katriel (iritkatriel) * |
Date: 2021-08-20 09:51 | |
I can't reproduce this now: >>> statistics.geometric_mean([2, 3, 5, 7]) 3.80675409583932 >>> statistics.geometric_mean([2, 3, 5, 7.0]) 3.80675409583932 >>> statistics.geometric_mean([2, 3, 5.0, 7.0]) 3.80675409583932 >>> statistics.geometric_mean([2, 3.0, 5.0, 7.0]) 3.80675409583932 >>> statistics.geometric_mean([2.0, 3.0, 5.0, 7.0]) 3.80675409583932 >>> The current geometric_mean was added in PR12638. Is this issue about a previous version? |
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| msg399951 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2021-08-20 10:02 | |
> Is this issue about a previous version? Yep. Sorry for failing to close this earlier. |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:58:37 | admin | set | github: 72514 |
| 2021-08-20 10:02:48 | mark.dickinson | set | status: open -> closed resolution: out of date messages: + msg399951 stage: resolved |
| 2021-08-20 09:51:12 | iritkatriel | set | nosy:
+ iritkatriel messages: + msg399948 |
| 2016-10-04 16:33:07 | steven.daprano | set | versions: - Python 3.6 |
| 2016-10-01 13:23:01 | mark.dickinson | set | files:
+ geometric_mean_int_float_v2.patch messages: + msg277815 |
| 2016-10-01 13:22:25 | steven.daprano | set | messages: + msg277814 |
| 2016-10-01 12:20:11 | mark.dickinson | set | files:
+ geometric_mean_int_float.patch keywords: + patch messages: + msg277809 |
| 2016-10-01 12:18:35 | mark.dickinson | create | |