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Created on 2018-07-18 17:31 by sir-sigurd, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Pull Requests | |||
|---|---|---|---|
| URL | Status | Linked | Edit |
| PR 8332 | merged | sir-sigurd, 2018-07-18 17:33 | |
| Messages (4) | |||
|---|---|---|---|
| msg321905 - (view) | Author: Sergey Fedoseev (sir-sigurd) * | Date: 2018-07-18 17:31 | |
Currently list concatenation, slicing and repeating operations are using PyList_New() which allocates memory for the items by calloc(). malloc() could be used instead, since the allocated memory is overwritten by mentioned operations. I made benchmarks with this script: NAME=list-malloc-master.json python -m perf timeit --name slice0 -s "l = [None]*1000000" "l[:0]" --duplicate=2048 --append $NAME python -m perf timeit --name slice1 -s "l = [None]*1000000" "l[:1]" --duplicate=1024 --append $NAME python -m perf timeit --name slice2 -s "l = [None]*1000000" "l[:2]" --duplicate=1024 --append $NAME python -m perf timeit --name slice3 -s "l = [None]*1000000" "l[:3]" --duplicate=1024 --append $NAME python -m perf timeit --name slice1000000 -s "l = [None]*1000000" "l[:1000000]" --append $NAME python -m perf timeit --name cat0 -s "l = [None]*0" "l + l" --duplicate=1024 --append $NAME python -m perf timeit --name cat1 -s "l = [None]*1" "l * 1" --duplicate=1024 --append $NAME python -m perf timeit --name cat2 -s "l = [None]*2" "l * 1" --duplicate=1024 --append $NAME python -m perf timeit --name cat3 -s "l = [None]*3" "l * 1" --duplicate=1024 --append $NAME python -m perf timeit --name cat1000000 -s "l = [None]*1000000" "l * 1" --append $NAME python -m perf timeit --name 1x0 -s "l = [None]" "l * 0" --duplicate=1024 --append $NAME python -m perf timeit --name 1x1 -s "l = [None]" "l * 1" --duplicate=1024 --append $NAME python -m perf timeit --name 1x2 -s "l = [None]" "l * 2" --duplicate=1024 --append $NAME python -m perf timeit --name 1x3 -s "l = [None]" "l * 3" --duplicate=1024 --append $NAME python -m perf timeit --name 1x1000000 -s "l = [None]" "l * 1000000" --append $NAME Here's comparison table: +--------------+--------------------+------------------------------+ | Benchmark | list-malloc-master | list-malloc | +==============+====================+==============================+ | slice1 | 84.5 ns | 59.6 ns: 1.42x faster (-30%) | +--------------+--------------------+------------------------------+ | slice2 | 71.6 ns | 61.8 ns: 1.16x faster (-14%) | +--------------+--------------------+------------------------------+ | slice3 | 74.4 ns | 63.6 ns: 1.17x faster (-15%) | +--------------+--------------------+------------------------------+ | slice1000000 | 4.39 ms | 4.08 ms: 1.08x faster (-7%) | +--------------+--------------------+------------------------------+ | cat0 | 23.9 ns | 24.9 ns: 1.04x slower (+4%) | +--------------+--------------------+------------------------------+ | cat1 | 73.2 ns | 51.9 ns: 1.41x faster (-29%) | +--------------+--------------------+------------------------------+ | cat2 | 61.6 ns | 53.1 ns: 1.16x faster (-14%) | +--------------+--------------------+------------------------------+ | cat3 | 63.0 ns | 54.3 ns: 1.16x faster (-14%) | +--------------+--------------------+------------------------------+ | cat1000000 | 4.38 ms | 4.08 ms: 1.07x faster (-7%) | +--------------+--------------------+------------------------------+ | 1x0 | 27.1 ns | 27.7 ns: 1.02x slower (+2%) | +--------------+--------------------+------------------------------+ | 1x1 | 72.9 ns | 51.9 ns: 1.41x faster (-29%) | +--------------+--------------------+------------------------------+ | 1x2 | 60.9 ns | 52.9 ns: 1.15x faster (-13%) | +--------------+--------------------+------------------------------+ | 1x3 | 62.5 ns | 54.8 ns: 1.14x faster (-12%) | +--------------+--------------------+------------------------------+ | 1x1000000 | 2.67 ms | 2.34 ms: 1.14x faster (-12%) | +--------------+--------------------+------------------------------+ Not significant (1): slice0 |
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| msg321914 - (view) | Author: Stefan Behnel (scoder) *  |
Date: 2018-07-18 20:07 | |
Nice! Patch looks good to me, minus the usual naming nit-pick. |
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| msg321925 - (view) | Author: Raymond Hettinger (rhettinger) * |
Date: 2018-07-19 05:27 | |
+1 This looks like a reasonable improvement. |
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| msg323415 - (view) | Author: Xiang Zhang (xiang.zhang) * |
Date: 2018-08-11 13:12 | |
New changeset 2fc46979b8c802675ca7fd51c6f2108a305001c8 by Xiang Zhang (Sergey Fedoseev) in branch 'master': bpo-34151: Improve performance of some list operations (GH-8332) https://github.com/python/cpython/commit/2fc46979b8c802675ca7fd51c6f2108a305001c8 |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:03 | admin | set | github: 78332 |
| 2018-08-11 13:14:26 | xiang.zhang | set | status: open -> closed resolution: fixed stage: patch review -> resolved |
| 2018-08-11 13:12:11 | xiang.zhang | set | nosy:
+ xiang.zhang messages: + msg323415 |
| 2018-07-19 06:19:13 | xtreak | set | nosy:
+ xtreak |
| 2018-07-19 05:27:15 | rhettinger | set | nosy:
+ rhettinger messages: + msg321925 |
| 2018-07-18 20:07:04 | scoder | set | nosy:
+ scoder messages: + msg321914 versions: + Python 3.8 |
| 2018-07-18 17:33:45 | sir-sigurd | set | keywords:
+ patch stage: patch review pull_requests: + pull_request7869 |
| 2018-07-18 17:31:49 | sir-sigurd | create | |