Re: Prioritizing non-dependent targets in parallel make

[tom honermann]

On 12/24/2009 2:37 AM, Tim Murphy wrote:
> Personally I don't like the idea of priorities very much.  Large
> builds that I have done do have big targets but since we are building
> 5000 of the same kind of target (using a macro to define a generic
> template and $eval to instantiate it for each specific target) it
> becomes impossible for us to provide hints.  In the end we'd have to
> force the users of our build system say  "webkit.dll" is pretty huge
> or  "euser.dll" isn't.  Since this is all relative information, how
> can we expect a build made up of components that various people
> produce to have the right "relative" weights?
>   
For specifying priorities for targets built by pattern rules, something 
like the following could
potentially be supported:

   %.DoMyThing: %.DirectoryOfUnpredictableSize
   priority -5 largedir.DoMyThing
   priority 5 smalldir.DoMyThing

Thus, you could do some optimization in this case.  I agree managing 
5000 targets in such
a way is not realistic, but specifying just a few could still impact 
build times favorably.  This
is actually one case where a learning system may not be desired - since 
it would (probably)
have to evaluate all 5000 targets.
> So I, personally, want something that learns.  I would like to be able
> to store the learned information into source control and use it as the
> basis for the next attempt.  One would have to check for patents on
> this, I think.
>   
Something that learns would definitely be nice.  Note that the syntaxes 
I proposed would be
amenable to a learning system - the learning system could produce make 
files with these rules
which could be included by other make files.  This is similar to what is 
often done with build
time generated dependencies.
> Regards,
>
> Tim
>
>