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Cmake ignoring option and compiling with just one thread (lemmy.ml)

submitted 2 months ago by [email protected] to c/[email protected]

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Using the -j option is ignored. About two weeks ago I found out that cmake was compiling with only one thread but everything was ok a couple of months ago. I'm using Debian Trixie which is still in testing so I thought it was a bug, but after many system updates I didn't saw cmake being updated. I couldn't find anything after a some searches. Another related issue is that I recently compiled a new version of a qt app with an edit box to set the number of threads for running LLMs, after the last compilation it doesn't allow to set more than one. Any clue?

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[–] [email protected] 2 points 2 months ago (1 children)

I know when I’m doing compiling myself, I add my ‘-j’ along with my make command. I’m a total noob at compiling so this may just be me not understanding that you can put it on either command.

[–] [email protected] 1 points 2 months ago

yeah, both have same the option, -j N lets you execute the compiling with N parallel jobs. In the case of make using -j without arguments it compiles without setting a limit for parallel jobs.

[–] [email protected] 2 points 3 weeks ago (1 children)

What build system are you using? Ninja is multithreaded by default so it will be ignored but systems like msbuild, Make, xcodebuild, iirc are single threaded by default and you can promote them to multi threaded by using -j or just passing their multithreaded option like

cmake --build <binarydir> --config Debug -- /m # msbuild

if cmake is actually ignoring the -j flag. If it is you should create a ticket on cmakes gitlab repo

[–] [email protected] 1 points 2 weeks ago

Both make and cmake are ignoring the j option and some of the software compiled with them also run in a single thread when they shouldn't, it seems a system problem, could it be an env variable?