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Update test command on dev guide landing page #1171
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This makes sense.
The linked "Run the tests" gives more info:
If you have a multi-core or multi-CPU machine, you can enable parallel testing using several Python processes so as to speed up things:
./python -m test -j0If you are running a version of Python prior to 3.3 you must specify the number of processes to run simultaneously (e.g.
-j2).Let's recommend
-j0on the landing page, and we could add more info for older/single-core machines to this longer description.And it's probably worth removing the "prior to 3.3" by now, 3.2 is EOL since 2016.
Reacted by Carol WillingIt is worth updating the GA of CPython too.
Reacted by Carol WillingSorry for my ignorance but how does -j0 differ from -j?
From the GNU docs :
If the ‘-j’ option is followed by an integer, this is the number of recipes to execute at once; this is called the number of job slots. If there is nothing looking like an integer after the ‘-j’ option, there is no limit on the number of job slots.
I just wondered why step 3 for build python uses -j and the recommendation for tests is -j0. What's the difference between them?
I'd be happy to have a go at this as a first contribution but just wanted to check my understanding.
There's some inconsistency in the
-joptions formakeand for./python -m test.On macOS:
❯ make -j8 Checked 107 modules (31 built-in, 76 shared, 0 n/a on macosx-13.6-arm64, 0 disabled, 0 missing, 0 failed on import) ❯ make -j Checked 107 modules (31 built-in, 76 shared, 0 n/a on macosx-13.6-arm64, 0 disabled, 0 missing, 0 failed on import) ❯ make -j0 make: the `-j' option requires a positive integral argument Usage: make [options] [target] ... Options: -b, -m Ignored for compatibility. -B, --always-make Unconditionally make all targets. -C DIRECTORY, --directory=DIRECTORY Change to DIRECTORY before doing anything. -d Print lots of debugging information. --debug[=FLAGS] Print various types of debugging information. -e, --environment-overrides Environment variables override makefiles. -f FILE, --file=FILE, --makefile=FILE Read FILE as a makefile. -h, --help Print this message and exit. -i, --ignore-errors Ignore errors from commands. -I DIRECTORY, --include-dir=DIRECTORY Search DIRECTORY for included makefiles. -j [N], --jobs[=N] Allow N jobs at once; infinite jobs with no arg. -k, --keep-going Keep going when some targets can't be made. -l [N], --load-average[=N], --max-load[=N] Don't start multiple jobs unless load is below N. -L, --check-symlink-times Use the latest mtime between symlinks and target. -n, --just-print, --dry-run, --recon Don't actually run any commands; just print them. -o FILE, --old-file=FILE, --assume-old=FILE Consider FILE to be very old and don't remake it. -p, --print-data-base Print make's internal database. -q, --question Run no commands; exit status says if up to date. -r, --no-builtin-rules Disable the built-in implicit rules. -R, --no-builtin-variables Disable the built-in variable settings. -s, --silent, --quiet Don't echo commands. -S, --no-keep-going, --stop Turns off -k. -t, --touch Touch targets instead of remaking them. -v, --version Print the version number of make and exit. -w, --print-directory Print the current directory. --no-print-directory Turn off -w, even if it was turned on implicitly. -W FILE, --what-if=FILE, --new-file=FILE, --assume-new=FILE Consider FILE to be infinitely new. --warn-undefined-variables Warn when an undefined variable is referenced. -N OPTION, --NeXT-option=OPTION Turn on value of NeXT OPTION. This program built for i386-apple-darwin11.3.0 Report bugs to <bug-make@gnu.org>
And:
❯ ./python.exe -m test -j8 == CPython 3.13.0a0 (heads/main:6ab6040054e5, Oct 5 2023, 08:37:40) [Clang 15.0.0 (clang-1500.0.40.1)] == macOS-13.6-arm64-arm-64bit little-endian == Python build: debug == cwd: /Users/hugo/github/cpython/build/test_python_worker_12564æ == CPU count: 8 == encodings: locale=UTF-8, FS=utf-8 == resources: (all disabled, use -u option) ... ❯ ./python.exe -m test -j0 == CPython 3.13.0a0 (heads/main:6ab6040054e5, Oct 5 2023, 08:37:40) [Clang 15.0.0 (clang-1500.0.40.1)] == macOS-13.6-arm64-arm-64bit little-endian == Python build: debug == cwd: /Users/hugo/github/cpython/build/test_python_worker_12634æ == CPU count: 8 == encodings: locale=UTF-8, FS=utf-8 == resources: (all disabled, use -u option) ... ❯ ./python.exe -m test -j usage: python -m test [options] [test_name1 [test_name2 ...]] python path/to/Lib/test/regrtest.py [options] [test_name1 [test_name2 ...]] regrtest.py: error: argument -j/--multiprocess: expected one argument Pass -h or --help for complete help.
makedoes not necessarily imply GNU Make; our makefile can also be run with BSD Make. Mybsdmakeonly accepts-jwith a positive integer argument.GNU Make:
-j [jobs], --jobs[=jobs] Specifies the number of jobs (commands) to run simultaneously. If there is more than one -j option, the last one is effective. If the -j option is given without an argument, make will not limit the number of jobs that can run simultaneously.BSD Make:
-j max_jobs Specify the maximum number of jobs that bsdmake may have running at any one time. Turns compatibility mode off, unless the B flag is also specified.So
-j0is the safe option for both thesemakes andpython -m test.
Separately, we can't easily change all these
makeflavours, but we could makepython -m testmore accepting and addpython -m test -jto do the same aspython -m test -j0?Thanks for the info
Hey, if the decision has been taken as specified by @willingc I would kindly love to work on this issue meanwhile let me be working on some other issue as I wait for this. Thanks
The quick reference currently has
./python -m test -j0, but https://devguide.python.org/testing/run-write-tests/#running has the parallel execution instructions buried well down the page.
On the landing page, we recommend running:
./python -m test -j3Since most systems now are multicore, we should consider recommending:
./python -m test -j0Tests on my machine several minutes faster. We could continue to recommend./python -m test -j3for folks using older or single-core machines.