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Created on 2009-05-10 17:29 by vstinner, last changed 2022-04-11 14:56 by admin. This issue is now closed.
| Files | ||||
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| File name | Uploaded | Description | Edit | |
| shuffle.patch | vstinner, 2009-05-10 17:29 | |||
| Messages (3) | |||
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| msg87531 - (view) | Author: STINNER Victor (vstinner) *  |
Date: 2009-05-10 17:29 | |
reversed(xrange(1, len(x))) is inefficient, xrange(len(x) - 1, 0, -1) gives exactly the same sequence but avoid reversed(). See attached patch. Don't expect amazing speedup. |
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| msg87563 - (view) | Author: Raymond Hettinger (rhettinger) * |
Date: 2009-05-11 07:12 | |
-1 on this patch. Reversed has a very low overhead. Readability if more important. The current code is self-evidently correct but the patched code is less obviously so. |
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| msg87565 - (view) | Author: Raymond Hettinger (rhettinger) * |
Date: 2009-05-11 07:44 | |
FWIW, the inefficiency is only in the loop setup, the time to call reversed() and __reversed__(). The inner loop runs at the same speed because xrange provides a __reversed__ iterator. Please do not go through the standard library making these minor tweaks without making sure there is a significant measured speed-up and do consider the readability issue. |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:56:48 | admin | set | github: 50236 |
| 2009-05-11 07:44:24 | rhettinger | set | status: open -> closed resolution: rejected messages: + msg87565 |
| 2009-05-11 07:13:00 | rhettinger | set | messages: + msg87563 |
| 2009-05-11 00:00:47 | benjamin.peterson | set | assignee: rhettinger nosy: + rhettinger |
| 2009-05-10 18:04:53 | pitrou | set | priority: normal stage: patch review type: performance versions: + Python 3.1, Python 2.7 |
| 2009-05-10 17:29:35 | vstinner | create | |