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Created on 2011-06-02 19:47 by rhettinger, last changed 2022-04-11 14:57 by admin. This issue is now closed.
| Files | ||||
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| File name | Uploaded | Description | Edit | |
| issue12245.patch | mark.dickinson, 2011-06-25 09:34 | review | ||
| Messages (6) | |||
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| msg137493 - (view) | Author: Raymond Hettinger (rhettinger) *  |
Date: 2011-06-02 19:47 | |
>>> sys.float_info.rounds 1 |
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| msg137647 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2011-06-04 15:14 | |
float_info.rounds is a bit of an odd fish, and I think it was probably a mistake to include it in sys.float_info in the first place.
All the other float_info fields relate to parameters of the floating-point format, which is fixed, useful information. In contrast, float_info.rounds gives information about the current FPU settings, which are variable. Moreover, it doesn't do that very well: all it does is give information about the FPU settings at the time that Python was compiled, which isn't really very helpful (and perhaps not even that: it reports the value of FLT_ROUNDS, which may not even reflect those FPU settings accurately). I wouldn't mind seeing this field fade quietly into obscurity.
FWIW, the value is taken from C's FLT_ROUNDS, and its interpretation is *supposed* to be the following (C99 5.2.4.2.2, para 7):
-1: The compiler was unable to determine rounding mode.
0: Round towards zero.
1: Round to nearest (this is the most likely value for
float_info.rounds on common platforms).
2: Round towards positive infinity
3: Round towards negative infinity.
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| msg139031 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2011-06-25 09:25 | |
> all it does is give information about the FPU settings at the time that > Python was compiled Hmm. It's actually a bit better than that: as far as I can tell, it reflects the value of FLT_ROUNDS at the time that Python is started (when the sys module is initialized). OTOH, FLT_ROUNDS on my machine is #define'd to be 1, in violation of the C standards. |
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| msg139032 - (view) | Author: Mark Dickinson (mark.dickinson) * |
Date: 2011-06-25 09:34 | |
Patch that elaborates a bit on the meaning of sys.float_info.rounds. |
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| msg147321 - (view) | Author: Ezio Melotti (ezio.melotti) * |
Date: 2011-11-08 23:38 | |
LGTM |
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| msg147949 - (view) | Author: Roundup Robot (python-dev)  |
Date: 2011-11-19 16:27 | |
New changeset de1ecda2afa2 by Mark Dickinson in branch '2.7': Issue #12245: Document sys.float_info.rounds better. http://hg.python.org/cpython/rev/de1ecda2afa2 New changeset 795c184b0282 by Mark Dickinson in branch '3.2': Issue #12245: Document sys.float_info.rounds better. http://hg.python.org/cpython/rev/795c184b0282 New changeset 5e45dfc421e4 by Mark Dickinson in branch 'default': Issue #12245 merge. http://hg.python.org/cpython/rev/5e45dfc421e4 |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:57:18 | admin | set | github: 56454 |
| 2011-11-19 16:28:16 | mark.dickinson | set | status: open -> closed resolution: fixed |
| 2011-11-19 16:27:50 | python-dev | set | nosy:
+ python-dev messages: + msg147949 |
| 2011-11-08 23:38:58 | ezio.melotti | set | nosy:
+ ezio.melotti messages: + msg147321 stage: commit review |
| 2011-06-25 09:34:25 | mark.dickinson | set | files:
+ issue12245.patch keywords: + patch messages: + msg139032 |
| 2011-06-25 09:25:52 | mark.dickinson | set | messages: + msg139031 |
| 2011-06-04 16:19:09 | mark.dickinson | set | assignee: docs@python -> mark.dickinson |
| 2011-06-04 16:18:06 | mark.dickinson | set | nosy:
+ christian.heimes |
| 2011-06-04 15:14:42 | mark.dickinson | set | nosy:
+ mark.dickinson messages: + msg137647 |
| 2011-06-02 19:47:10 | rhettinger | create | |