New submission from Sergey Fedoseev <[email protected]>:
list_slice() is used by PyList_GetSlice(), list_subscript() and for list
copying. In list_subscript() slice indices are already normalized with
PySlice_AdjustIndices(), so slice normalization currently performed in
list_slice() is only needed for PyList_GetSlice(). Moving this normalization
from list_slice() to PyList_GetSlice() provides minor speed-up for list copying
and slicing:
$ python -m perf timeit -s "copy = [].copy" "copy()" --duplicate=1000
--compare-to=../cpython-master/venv/bin/python
/home/sergey/tmp/cpython-master/venv/bin/python: ..................... 26.5 ns
+- 0.5 ns
/home/sergey/tmp/cpython-dev/venv/bin/python: ..................... 25.7 ns +-
0.5 ns
Mean +- std dev: [/home/sergey/tmp/cpython-master/venv/bin/python] 26.5 ns +-
0.5 ns -> [/home/sergey/tmp/cpython-dev/venv/bin/python] 25.7 ns +- 0.5 ns:
1.03x faster (-3%)
$ python -m perf timeit -s "l = [1]" "l[:]" --duplicate=1000
--compare-to=../cpython-master/venv/bin/python
/home/sergey/tmp/cpython-master/venv/bin/python: ..................... 71.5 ns
+- 1.4 ns
/home/sergey/tmp/cpython-dev/venv/bin/python: ..................... 70.2 ns +-
0.9 ns
Mean +- std dev: [/home/sergey/tmp/cpython-master/venv/bin/python] 71.5 ns +-
1.4 ns -> [/home/sergey/tmp/cpython-dev/venv/bin/python] 70.2 ns +- 0.9 ns:
1.02x faster (-2%)
----------
messages: 336184
nosy: sir-sigurd
priority: normal
severity: normal
status: open
title: move index normalization from list_slice() to PyList_GetSlice()
type: performance
versions: Python 3.8
_______________________________________
Python tracker <[email protected]>
<https://bugs.python.org/issue36062>
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