[issue34152] performance of some list slice assignment can be improved

[Sergey Fedoseev]

Change by Sergey Fedoseev :


--
keywords: +patch
pull_requests: +7870
stage:  -> patch review

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[issue34152] performance of some list slice assignment can be improved

[Sergey Fedoseev]

New submission from Sergey Fedoseev :

Script for benchmarks:

NAME=list-slice.json

python -m perf timeit --name "l[len(l):] = reversed(l)" -l 1 -s "l = [None] * 
100" "l[len(l):] = reversed(l)" --append $NAME
python -m perf timeit --name "l[len(l):] = l" -l 1 -s "l = [None] * 100" 
"l[len(l):] = l" --append $NAME
python -m perf timeit --name "l[::-1] = l" -s "l = [None] * 100" "l[::-1] = 
l" --append $NAME
python -m perf timeit --name "l[:] = l" -s "l = [None] * 100" "l[:] = l" 
--append $NAME
python -m perf timeit --name "l[len(l)//2:] = l" -l 1 -s "l = [None] * 100" 
"l[len(l)//2:] = l"  --append $NAME
python -m perf timeit --name "l[:len(l)//2] = l" -l 1 -s "l = [None] * 100" 
"l[:len(l)//2] = l" --append $NAME
python -m perf timeit --name "l[len(l)//4:len(l)*3//4] = l" -l 1 -s "l = [None] 
* 100" "l[len(l)//4:len(l)*3//4] = l" --append $NAME

Results table:

+--+---++
| Benchmark| list-slice-master | list-slice 
|
+==+===++
| l[len(l):] = reversed(l) | 8.44 ms   | 5.18 ms: 1.63x faster 
(-39%)   |
+--+---++
| l[len(l):] = l   | 7.88 ms   | 3.37 ms: 2.34x faster 
(-57%)   |
+--+---++
| l[::-1] = l  | 10.4 ms   | 582 us: 17.85x faster 
(-94%)   |
+--+---++
| l[:] = l | 10.6 ms   | 86.1 ns: 123128.46x faster 
(-100%) |
+--+---++
| l[len(l)//2:] = l| 11.1 ms   | 2.08 ms: 5.33x faster 
(-81%)   |
+--+---++
| l[:len(l)//2] = l| 11.5 ms   | 1.76 ms: 6.53x faster 
(-85%)   |
+--+---++
| l[len(l)//4:len(l)*3//4] = l | 11.3 ms   | 2.27 ms: 4.98x faster 
(-80%)   |
+--+---++

--
components: Interpreter Core
messages: 321908
nosy: sir-sigurd
priority: normal
severity: normal
status: open
title: performance of some list slice assignment can be improved
type: performance

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