"Daniel J. Luke" <dluke@geeklair.net> writes:

The -j is actually a make option.

The make manpage describes it like this: -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.

I believe the idea is that the user can specify the number of simultaneous jobs they want, and if a port has this flag it will pass the appropriate -j N (where N is the number of jobs) to make. At some point, macports will probably be updated to detect a good default value for N (that the user could override), but I don't believe that there's code for that yet.

Weissmann Markus <mww@macports.org> writes:

I've just added a way to automatically set the number of build jobs (if desired): If the number of build jobs is set to "0" (in the config file), the number of jobs is set to the number of cores.

This works only on Mac OS X (and FreeBSD -- though untested).

I pasted the raw text from my latest doc update on "use_parallel_build". Is this accurate? use_parallel_build This keyword is for specifying whether or not it is safe for a port to use multiple cpus or multiple cores in parallel during its build phase. This keyword passes the -j [jobs] option to make, where jobs is obtained from the variable buildmakejobs in macports.conf. This variable may also be set to 0 so the number of jobs is set to the number of cores detected during the build phase. Mark