[Scons-users] Clone effectiveness

[Hua Yanghao]

I see. I solve this problem by defining and creating only new env for
a build at top level, and never creating new env in SConscript.
e.g. all SConscript is using a common pre-defined env, but one
SConscript can be used by multiple env.

This way my number of env is equal to the number of build target I have.
On Fri, Sep 14, 2018 at 4:19 PM Gary Oberbrunner <garyo at oberbrunner.com> wrote:
>
> Overrides aren't expensive. Go ahead & use them, pass keyword flags to builders etc.
> But let's say you have a sub-SConscript that must use a different compiler for everything in that subdir. Typical use is to import the main env, clone it, and modify for all the targets in that sub-SConscript.
>
> On Fri, Sep 14, 2018 at 9:41 AM Hua Yanghao <huayanghao at gmail.com> wrote:
>>
>> But seems passing flags also does similar thing with override?
>>
>> What must be changed in the env that cannot be done with ovrride? as
>> majority of the builds are based on variable substitution.
>> On Fri, Sep 14, 2018 at 3:12 PM Gary Oberbrunner <garyo at oberbrunner.com> wrote:
>> >
>> > Most people use them in a sub-SConscript so they can make changes to the env in that script that don't propate up to the calling SConstruct. Not the only use case of course, but a popular one.
>> >
>> > -- Gary
>> >
>> > On Fri, Sep 14, 2018 at 8:15 AM Hua Yanghao <huayanghao at gmail.com> wrote:
>> >>
>> >> Thanks Gary.
>> >>
>> >> In this case I think I am mostly using overrides, and only one env per
>> >> software image build.
>> >>
>> >> If we have overrides what are the scenarios that a Clone() of the env
>> >> is a must to have?
>> >> On Fri, Sep 14, 2018 at 2:03 PM Gary Oberbrunner <garyo at oberbrunner.com> wrote:
>> >> >
>> >> > No. It may create an override internally, if you pass some keyword args, but that's not a clone. So you can call Object() thousands of times for sure.
>> >> >
>> >> > -- Gary
>> >> >
>> >> > On Fri, Sep 14, 2018 at 7:56 AM Hua Yanghao <huayanghao at gmail.com> wrote:
>> >> >>
>> >> >> Is every call to "Object()" implicitly creates a clone of environment?
>> >> >> I seems like so just want to confirm.
>> >> >> On Thu, Sep 13, 2018 at 9:20 PM Mats Wichmann <mats at wichmann.us> wrote:
>> >> >> >
>> >> >> > On 09/13/2018 12:52 PM, Damien Hocking wrote:
>> >> >> > > We do this too.  Most dlls and sos have a cloned environment.
>> >> >> >
>> >> >> > As I said earlier, we clone lots (>90% of our sconscripts contain a
>> >> >> > Clone() call), but the actual build time dwarfs the "process the
>> >> >> > SConscripts" phase (*) so I don't worry much about it. We're not getting
>> >> >> > killed on memory; I can build easily enough in a 2gb Vagrant-provisioned
>> >> >> > (Linux) image. So while I'd like to *know* the numbers, it's mostly
>> >> >> > curiosity.
>> >> >> >
>> >> >> > Maybe we can resurrect some of the benchmarking/timing code that exists
>> >> >> > in the codebase now to get more info?
>> >> >> >
>> >> >> > * - recent build timings:
>> >> >> > Total build time: 360.533189 seconds  (using scons -j4)
>> >> >> > Total SConscript file execution time: 14.785102 seconds
>> >> >> >
>> >> >> > 15 seconds is slow, but if I sped up the sconscript time by 50%, I'd
>> >> >> > still make no more than a 2% impact on the overall time.
>> >> >> >
>> >> >> > >> On Sep 13, 2018, at 12:27 PM, Pierre-Luc Boily <pierreluc.boily at gmail.com> wrote:
>> >> >> > >>
>> >> >> > >> Hello!
>> >> >> > >>
>> >> >> > >> Just read on the forum :
>> >> >> > >>
>> >> >> > >> /Here's the caveat.
>> >> >> > >> Don't make a gazillion Clone's they're not lightweight.
>> >> >> > >> If you make 100, it won't kill you, if you make 1000's you may start seeing
>> >> >> > >> memory and speed impacted./
>> >> >> > >>
>> >> >> > >> Our project branch contains 800 sconscript files.  From those 800, 300 are
>> >> >> > >> for windows compilation, 500 are for unix compilation.
>> >> >> > >>
>> >> >> > >> We systematically create a clone of the environment at the beginning of
>> >> >> > >> *each *sconscript.  So, if I understand well, it might not be the best
>> >> >> > >> approach.  It would be better to do a Clone only when it is needed?
>> >> >> > >> Reducing the number of clone could potentially speed up the creating of the
>> >> >> > >> tree?
>> >> >> > >>
>> >> >> > >> Thx
>> >> >> > >>
>> >> >> > >>
>> >> >> > >>
>> >> >> > >> --
>> >> >> > >> Sent from: http://scons.1086193.n5.nabble.com/Users-f16930.html
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>> >> >
>> >> > --
>> >> > Gary
>> >> > _______________________________________________
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>> > --
>> > Gary
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>
>
> --
> Gary
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