[MacPorts] #25507: kdelibs4 4.4.x fails to compile/link: undefined symbols "_png_set_longjmp_fn"

[Ryan Schmidt]

On Jul 9, 2010, at 17:18, Jeremy Lavergne wrote:

> It seems that the i5 processor convinces MacPorts it can do 4 make jobs at a time. Is this expected MacPorts behavior?

Yes, that sounds normal.

MacPorts starts as many jobs as possible, with the following limits:

One job per available processor or core or thread, up to one job per GB of memory in the machine.

So if you have at least 4 GB RAM and a hyperthreaded dual-core i5, then you will have 4 jobs running. If the port cannot handle this, the port should disable parallel building.

I once suggested it would be a good idea to replace the "use_parallel_build" yes/no switch with a more fine-grained switch (say "parallel_jobs") where you could specify the maximum number of parallel jobs. "parallel_jobs 1" would then be the equivalent of today's "use_parallel_build no", "parallel_jobs 0" could be the equivalent of today's "use_parallel_build yes" (mirrors the way "buildmakejobs" works in macports.conf today), and for example "parallel_jobs 2" could be used for ports that support 2 parallel jobs but not more. But for now we don't have this, so software must either support any arbitrary number of parallel jobs, or not be run in parallel at all.