[libcxx-dev] Parallel STL

[Christopher Nelson via libcxx-dev]

Fantastic. I will study the serial backend and see what I can do!

On Tue, Sep 15, 2020 at 5:27 PM Louis Dionne <ldionne at apple.com> wrote:

> + Mikhail, who wrote most of the PSTL
>
> On Sep 15, 2020, at 15:40, Christopher Nelson <nadiasvertex at gmail.com>
> wrote:
>
> Okay, that makes sense. I can see how you might want to use Grand Central
> Dispatch on macOS, and the Windows system thread pool on Windows. I'm not
> really sure what that means for Linux, though. Other than maybe pthreads,
> which is not great.
>
> Is there any documentation on what is needed to create a backend? Or are
> there perhaps already plans in motion? I don't want to step on any toes,
> but I would love to have a usable pstl on macOS and Linux for the next LLVM
> release.
>
> We use libc++ on Linux as well as macOS. Depending on what's involved, I
> might be able to contribute a backend for those two platforms.
>
>
> You're not stepping on any toes, far from that. If we have backends with
> satisfactory performance and we're confident about ABI stability, I don't
> see a reason why we wouldn't ship the PSTL as soon as we have those. One
> big issue to shipping it so far has been that the only backends are serial
> (not great to ship that), and the other one relies on an external
> dependency (TBB).
>
> Mikhail might be able to provide documentation. We should check it into
> the PSTL repository. I meant to write such documentation when I wrote the
> serial backend, but never got around to writing something that was enough
> to check in. You can see the minimal API needed to implement a backend
> here: pstl/include/pstl/internal/parallel_backend_serial.h. It's the serial
> backend, which tries to be as trivial as possible.
>
> Are you familiar with libc++ contribution? If so, contributing to PSTL
> works basically the same -- just send a Phabricator review and I'll review
> it. We can also chat on Slack in the Cpplang workspace and I can give some
> guidance -- look for "ldionne".
>
> Cheers,
> Louis
>
>
> On Tue, Sep 15, 2020 at 2:50 PM Louis Dionne <ldionne at apple.com> wrote:
>
>> Hi,
>>
>> Long story short, the PSTL is pretty much ready to be shipped with LLVM.
>> I did the integration between it and libc++, and it all worked last time I
>> checked. I think the next step would be to change whatever LLVM scripts are
>> used to create releases to also install the PSTL, which is the part I
>> haven't had time to look into yet.
>>
>> That being said, the PSTL will then default to using the Serial backend,
>> which isn't very useful. We could decide to ship a different backend if we
>> wanted, however I think what makes sense is to use a backend specific to
>> the platform we're running on instead of adding a dependency to LLVM.
>>
>> Louis
>>
>> > On Sep 8, 2020, at 08:25, Christopher Nelson via libcxx-dev <
>> libcxx-dev at lists.llvm.org> wrote:
>> >
>> > Hello friends,
>> >
>> > I have spent some time looking at the mailing archives and git logs for
>> the parallel STL. I'm not clear what state it is in, since the oneAPI/tbb
>> seems to be production ready and comes with the parallel STL. Also, it
>> appears the GCC has shipped a PSTL based on the same code that clang is
>> using.
>> >
>> > I was wondering if someone could clarify for me what state the PSTL is
>> in, and if there is some work needed to help get it over the finish line I
>> may be able to help. I'm very interested in using it in our production
>> software, so I'm a motivated helper. :-)
>> >
>> > Thank you for your time,
>> > -={C}=-
>> > _______________________________________________
>> > libcxx-dev mailing list
>> > libcxx-dev at lists.llvm.org
>> > https://lists.llvm.org/cgi-bin/mailman/listinfo/libcxx-dev
>>
>>
>
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