Re: [OctDev] Improving pkg.m

[Paul D. <sl...@pa...>]

2012-09-24 01:59, Claudio Freire skrev:
> On Sun, Sep 23, 2012 at 6:29 PM, Paul Dreik <sl...@pa...> wrote:
>>> I just added:
>>>  make pkg able to supply extra configure and make flags, useful for
>>> distributions, including -j for make
>> Just curios, are there any octave packages that benefit from parallel
>> compilation?
> 
> Well, for openSUSE, we build all packages at once, and it takes a very
> long time, like an hour and a half, for about 80 packages. That's an
> average build time of a minute per package, big enough to make a
> difference with parallel compilation.
> 
> I actually haven't tried though, convincing pkg.m to add extra flags
> wasn't documented and seemed left out. Packaging would benefit from
> being able to send config and make-time flags, besides the parallel
> compilation aspect. Things like CFLAGS, for instance.
> 
I think this is good and I do not oppose it at all! My thought was that
make -j makes child processes of make run in parallel, which is
different from having several instances of make run in parallel.
That is why I asked if there is a package that improves from it - I
guess a package has to use multiple source files, where at least some
are nondependent so they can be compiled in parallel.

One could of course imagine a situation where a Makefile spanning
several packages is possible, made from the dependency information in
the packages. Invoking make at the root of the package tree would
certainly improve package generation if -j is used for that make
invokation. But that is maybe what you do for opensuse?

@Stephen:
no, I did not mean the benefit was negligible, I meant if -j would make
any difference at all because it requires the build to be possible to
parallelize.

@Juan Pablo:
You answered my question! I tried with -j4 and the compilation time
dropped certainly dropped, but only when the slicot library has been
built. Below, the "real" time output from the time command is used:
cd control/src
time make
72 seconds
make clean (to get the caches warm. note, make clean does not remove
slicotlibrary.a. Maybe it should?)
time make
18 seconds
make clean
time make -j4
12 seconds
make clean
rm slicotlibrary.a
time make -j4
63 seconds


Paul