[Question] Why is test_fast.sh configured to work with only 4 cores ?

[adrienpacifico]

• I have checked that the answer to this question is not present in any other issue, merge request comments, or the documentation.

test_fast.sh is the recommended way to run the test suite in an efficient manner.
However, it is configure to run only on 4 cores? Why?

Many modern computer has more than 4 cores. I would suggest to replace -n 4 to -n0 on the following test_fast.sh line

pandas/test_fast.sh

Line 8 in 65af4ef

pytest pandas --skip-slow --skip-network --skip-db -m "not single_cpu" -n 4 -r sxX "$@"

@mroeschke was the last to commit on that file (https://github.com/pandas-dev/pandas/blame/main/test_fast.sh) (it case it changes something for triage).

[mroeschke]

Thanks for the report. IMO since these scripts are so short, I would recommend removing them and just documenting the command with the note on how -n can be adjusted to the number of cores on the user's machine.

[adrienpacifico]

Thank you!
I see your point.

Just to report my experience. When I tried to run the tests for the first time, I ran the test_fast.sh file before reading the documentation. If I had not find that file, I would probably have ran pytest without these interesting options.

I think the -n0 option is improving most user situation without changing much their current workflow?
However, that does not seem very important!

[mroeschke]

I think the -n0 option is improving most user situation without changing much their current workflow?

I suppose so. I have just found local development to be just a broad topic that maintaining the documentation on guiding users on how to prepare their environment for contribution easier than maintaining several scripts & misc tools that are "opinionated" since a user setups can be widely varied.

[rhshadrach]

+1 for removal provided we're documenting the command in the contributing guide. I think it would be good to briefly describe what the options do (or at least link to pytest's documentation); I personally am not a fan of the -r sxX bit.

[WillAyd]

+1 to remove this script as well