[MacPorts] #58932: py-tensorflow: reduce build time

[MacPorts]

#58932: py-tensorflow: reduce build time
----------------------------+--------------------------
  Reporter:  ryandesign     |      Owner:  emcrisostomo
      Type:  enhancement    |     Status:  assigned
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:
Resolution:                 |   Keywords:
      Port:  py-tensorflow  |
----------------------------+--------------------------

Comment (by ryandesign):

 How much memory does your MBP have? I'm guessing more than 8 GB.

 Hopefully the tensorflow build process is already respecting the value of
 `build.jobs` but I'm not sure what a reasonable number of parallel jobs is
 for tensorflow. MacPorts sets `build.jobs` with the assumption that each
 compiler process might use up to 1 GB memory and that there should be an
 available core for each compiler process so on a machine with 8 cores and
 8 GB RAM it will allow 8 parallel jobs. This seems to work for most ports
 but there is the odd port that requires much more memory to build, like
 tensorflow. If bazel can be told to keep its memory usage to fit within
 the amount of memory that the machine has that could help. Otherwise it
 might be a start if the portfile could set `build.jobs` to a fraction of
 itself, for example:

 {{{
 if {${build.jobs} > 1} {
     build.jobs      [expr {${build.jobs} / 2}]
 }
 }}}

 That would reserve 2 GB per job instead of 1. Or a more complicated
 formula could be used based on the amount of RAM in the machine if you can
 figure out a simple way to determine what that is and what a good formula
 would be.

-- 
Ticket URL: <https://trac.macports.org/ticket/58932#comment:6>
MacPorts <https://www.macports.org/>
Ports system for macOS