Count leading zero bits in one CPU tick #19633

hnarkaytis · 2020-04-21T10:22:08Z

Count of leading bits was implemented as a CPU instructing 6 years ago. It doesn't make sense to have custom code for this.
https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_(Advanced_Bit_Manipulation)

the-knights-who-say-ni · 2020-04-21T10:22:11Z

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remilapeyre

Is this supported on all architecture that Python support (https://www.python.org/download/other/)?
What about CPU that don't have this instruction or where this instruction is slower?
Also this would need to be compatible with all compilers supported by CPython.

…nto count_leading_zeros

mdickinson · 2020-04-21T19:17:16Z

Python runs on many different platforms and architectures. It's written (mostly) in standard C (specifically, C89, but with some C99 features permitted). __builtin_clz is not part of standard C.

It's okay to have platform-specific code when there's a good reason for it, but there will still need to be fallback code for platforms that don't have __builtin_clz available: we can't simply assume that it'll be available on any non-Windows platform.

Python/pymath.c

…() (python#19634) Co-Authored-By: Victor Stinner <vstinner@python.org>

* Add underscores to long numbers to improve readability * Use bigger dataset in the bootstrapping example * Convert single-server queue example to more useful multi-server queue

…ms() loop (pythonGH-19628)

…onGH-19642)

Icon author: Andrew Clover, bpo-1490384

…16480) It is possible to use either '-isysroot /some/path' (with a space) or '-isysroot/some/path' (no space in between). Support both forms in places where special handling of -isysroot is done, rather than just the first form. Co-authored-by: Ned Deily <nad@python.org>

…thonGH-19650) Previously, python.org macOS installers did not alter the Current version symlink in /Library/Frameworks/Python.framework/Versions when installing a version of Python 3.x, only when installing 2.x. Now that Python 2 is retired, it's time to change that. This should make it a bit easier to embed Python 3 into other macOS applications.

mdickinson · 2020-04-22T12:59:57Z

@hnarkaytis Thanks for the contribution. If you want to pursue this further, there are a couple of steps you need to take:

Please could you open a corresponding issue on the bug tracker (https://bugs.python.org/)? At the moment, we don't use GitHub issues, so bugs.python.org is where any related discussion should take place.
Please sign the CLA agreement (see the automated messages above) if you haven't done so already.

See the Python Developer's Guide for more detailed information and guidelines on contributing to core Python.

hnarkaytis · 2020-04-22T13:18:01Z

@mdickinson let me take care of this.
I will extend configure for __builtin_clzl autodetection and will add fallback implementation for outdated compilers.

HHN.

@hnarkaytis Thanks for the contribution. If you want to pursue this further, there are a couple of steps you need to take:

Please could you open a corresponding issue on the bug tracker (https://bugs.python.org/)? At the moment, we don't use GitHub issues, so bugs.python.org is where any related discussion should take place.

Please sign the CLA agreement (see the automated messages above) if you haven't done so already.

See the Python Developer's Guide for more detailed information and guidelines on contributing to core Python.

mdickinson · 2020-04-22T13:24:20Z

See also https://bugs.python.org/issue29782 and PR #594.

Fix the Windows implementation of os.waitpid() for exit code larger than "INT_MAX >> 8". The exit status is now interpreted as an unsigned number. os.waitstatus_to_exitcode() now accepts wait status larger than INT_MAX.

…9230) The constant values of future flags in the __future__ module is updated in order to prevent collision with compiler flags. Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION.

…onGH-19774) After parsing is done in single statement mode, the tokenizer buffer has to be checked for additional lines and a `SyntaxError` must be raised, in case there are any. Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

…GH-19783) They were removed from the C API in commit ae00a5a.

ned-deily · 2020-04-29T06:34:42Z

@hnarkaytis, sorry but if you want anyone to review your suggestions, you need to follow our process as @mdickinson explained. And you need to redo this PR so it is against the current top of the master branch only, such that it only shows the actual changes you propose, not all the merges in 372 files.

hnarkaytis · 2020-04-29T06:49:16Z

@hnarkaytis, sorry but if you want anyone to review your suggestions, you need to follow our process as @mdickinson explained. And you need to redo this PR so it is against the current top of the master branch only, such that it only shows the actual changes you propose, not all the merges in 372 files.

Yeah - I know. Just pushed code first. Will get the rest shortly. I converted pull request to draft, so it should not trigger anyone in review list.

Count leading zero bits in one CPU tick

36b718d

the-knights-who-say-ni added the CLA not signed label Apr 21, 2020

bedevere-bot added the awaiting review label Apr 21, 2020

remilapeyre reviewed Apr 21, 2020

View reviewed changes

hnarkaytis added 4 commits April 21, 2020 19:53

Count leading zero bits in one CPU tick

5414a2f

Merge branch 'count_leading_zeros' of github.com:hnarkaytis/cpython i…

9b30a64

…nto count_leading_zeros

Add support for _MSC_

7e982dc

Workaround _MCVC_ support

debeb02

mdickinson reviewed Apr 21, 2020

View reviewed changes

Python/pymath.c Outdated Show resolved Hide resolved

aeros and others added 13 commits April 21, 2020 16:50

bpo-34037: Add Python API whatsnew for loop.shutdown_default_executor…

9c82ea7

…() (python#19634) Co-Authored-By: Victor Stinner <vstinner@python.org>

Small improvements to the recipes and examples. (pythonGH-19635)

d3a8d61

* Add underscores to long numbers to improve readability * Use bigger dataset in the bootstrapping example * Convert single-server queue example to more useful multi-server queue

bpo-40327: Improve atomicity, speed, and memory efficiency of the ite…

75bedbe

…ms() loop (pythonGH-19628)

bpo-40164: Update macOS installer builds to use OpenSSL 1.1.1g. (pyth…

783a673

…onGH-19642)

Workaround _MCVC_ inability to handle macro

939e4c1

bpo-38439: Add 256px IDLE icon (pythonGH-17473)

3a69f3c

Icon author: Andrew Clover, bpo-1490384

Count leading zero bits with single CPU instruction

9e2e2f3

Replace __builtin_clz with __builtin_clzl

22141ec

Change preprocessor check on ifdef MS_WINDOWS

886a15b

Add debug preprocessor check on ifdef MS_WINDOWS

bd95e34

Fix typo and argument type

543e481

vstinner and others added 3 commits April 22, 2020 16:30

bpo-40214: Fix ctypes WinDLL test with insecure flags (pythonGH-19652)

9b49893

bpo-39562: Prevent collision of future and compiler flags (pythonGH-1…

4454057

…9230) The constant values of future flags in the __future__ module is updated in order to prevent collision with compiler flags. Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing with CO_FUTURE_DIVISION.

lysnikolaou and others added 4 commits April 29, 2020 02:42

bpo-40428: Remove references to Py*_ClearFreeList in the docs (python…

bb4a585

…GH-19783) They were removed from the C API in commit ae00a5a.

Count leading zero bits in one CPU tick

8f36fda

Rebase to master

64ecf0d

hnarkaytis requested review from 1st1, asvetlov, berkerpeksag, brettcannon, encukou, ericsnowcurrently, ethanfurman, gpshead, gvanrossum, ilevkivskyi, methane, ncoghlan, pablogsal, rhettinger, terryjreedy, tiran, vsajip, warsaw and a team as code owners April 29, 2020 05:14

Cleanup merge conflict artifacts

2908911

hnarkaytis marked this pull request as draft April 29, 2020 06:26

terryjreedy closed this Apr 29, 2020

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