[llvm-dev] [Openmp-dev] [cfe-dev] RFC: Proposing an LLVM subproject for parallelism runtime and support libraries

Andrey Bokhanko via llvm-dev llvm-dev at lists.llvm.org
Thu Apr 28 06:23:06 PDT 2016


Very nice write-up. Well done!

My two kopecks (before you asked, one kopeck is the smallest item of
currency in Russia ;-)):
* Bugzilla and mailing list requirements are not covered. Do you want to
have a component in Bugzilla for each project? One for all of them? Mailing
list -- a separate list for each project? (IMHO, an overkill) One for all
of them?
* Build system -- I suppose you expect all of the libs to be built
separately, without a single unified cmake file. Correct? Also, I expect
you want all of the libs to be integrated into LLVM build -- correct? This
should be spelled out explicitly.
* I don't really like "parallel" in the name. Both SE and libomptarget are
libraries that handle offloading, not parallelism. I understand other
libraries, to be added in the future, might deal with parallelism, but
maybe we need a separate project for them? (Something Chris already
hinted.) How about "offloading_lib"?


On Wed, Apr 27, 2016 at 7:58 PM, Jason Henline via Openmp-dev <
openmp-dev at lists.llvm.org> wrote:

> I've put together a proposed "charter" for this new project, which I am
> calling parallel_utils (although I'm very open to suggestions for a better
> name). The text of my charter is below, and I welcome any input on how it
> can be improved.
> =====================================================
> LLVM Parallel Utils Subproject Charter
> =====================================================
> ----------------------------------------------
> Description
> ----------------------------------------------
> The LLVM open source project will contain a subproject named
> `parallel_utils` which will host the development of libraries which are
> aimed at enabling parallelism in code and which are also closely tied to
> compiler technology.  Examples of libraries suitable for hosting within the
> `parallel_utils` subproject are runtime libraries and parallel math
> libraries. The initial candidates for inclusion in this subproject are
> StreamExecutor and libomptarget which would live in the `streamexecutor`
> and `libomptarget` subdirectories of `parallel_utils`, respectively.
> The `parallel_utils` project will host a collection of libraries where
> each library may be dependent on other libraries from the project or may be
> completely independent of any other libraries in the project. The rationale
> for hosting independent libraries within the same subproject is that all
> libraries in the project are providing related functionality that lives at
> the intersection of parallelism and compiler technology. It is expected
> that some libraries which initially began as independent will develop
> dependencies over time either between existing libraries or by extracting
> common code that can be used by each. One of the purposes of this
> subproject is to provide a working space where such refactoring and code
> sharing can take place.
> Libraries in the `parallel_utils` subproject may also depend on the LLVM
> core libraries. This will be useful for avoiding duplication of code within
> the LLVM project for common utilities such as those found in the LLVM
> support library.
> ----------------------------------------------
> Requirements
> ----------------------------------------------
> Libraries included in the `parallel_utils` subproject must strive to
> achieve the following requirements:
> 1. Adhere to the LLVM coding standards.
> 2. Use the LLVM build and test infrastructure.
> 3. Be released under LLVM's license.
> Coding standards
> ----------------
> Libraries in `parallel_utils` will match the LLVM coding standards. For
> existing projects being checked into the subproject as-is, an exception
> will be made during the initial check-in, with the understanding that the
> code will be promptly updated to follow the standards. Therefore, a three
> month grace period will be allowed for new libraries to meet the LLVM
> coding standards.
> Additional exceptions to strict adherence to the LLVM coding standards may
> be allowed in certain other cases, but the reasons for such exceptions must
> be discussed and documented on a case-by-case basis.
> LLVM build and test infrastructure
> ----------------------------------
> Using the LLVM build and test infrastructure currently means using `cmake`
> for building, `lit` for testing, and `buildbot` for automating build and
> testing. This project will follow the main LLVM project conventions here
> and track them as they evolve.
> LLVM license
> ------------
> For simplicity, the `parallel_utils` project will use the normal LLVM
> license. While some runtime libraries use a dual license scheme in LLVM, we
> anticipate the project removing the need for this eventually and in the
> interim follow the simpler but still permissive license. Among other
> things, this makes it straightforward for these libraries to re-use core
> LLVM libraries where appropriate.
> On Wed, Apr 27, 2016 at 9:52 AM Jason Henline <jhen at google.com> wrote:
>> Andrey,
>> I may have misunderstood Chandler, but I think it would be good to house
>> libomptarget together with SE in the new project. I suspect he means to
>> leave the option open for the libomptarget developers to choose the best
>> option as they see fit.
>> In terms of organization, I would expect the project initially to contain
>> a StreamExecutor directory and a libomptarget directory where each project
>> could work separately.
>> When it comes to the difference in review process between the two
>> projects, I don't know the answer. I would expect the new project to handle
>> reviews similar to the way they are handled in the LLVM project itself, so
>> I don't know if there would be any difference compared to what is happening
>> now with libomptarget.
>> On Wed, Apr 27, 2016 at 9:32 AM C Bergström <openmp-dev at lists.llvm.org>
>> wrote:
>>> I respect Hal's more tactful approach and response..
>>> Let me play devils advocate for a minute
>>> 1) Yet another programming model - Is the advantage spelled out
>>> somewhere? (I know there are reasons, but I'd like to see a FAQ or
>>> this clearly documented. Examples pretty please.. More for long term
>>> than my own selfish benefit)
>>> 2) Is this an "open standard" - If I wanted to propose a major change
>>> to SE - how would I or someone else go about it? OpenMP/ACC have more
>>> or less clearly defined paths for new features.. What's the governing
>>> policy here.. Bug fixes are easy to deal with, but does Google have
>>> final say on the roadmap..
>>> 3) When the project is created - will it include lots of good tests?
>>> 4) It's probably used internally @google - who else will be using
>>> this? Is the target HPC, Android.. etc
>>> Lastly - sorry, but I don't like this kick-the-can approach to what
>>> should be proper engineering and planning upfront. Can someone @google
>>> gentleman's promise to actively work on playing nice with other
>>> projects, specifically OpenMP and Intel. From my perspective nothing
>>> stops Google from tossing it up on github or google code and letting
>>> it stay there until all the pieces are in the correct place. Why it
>>> *must* be an llvm project now doesn't make sense to me. When the shoe
>>> was on the other foot (OpenMP) there was all sorts of shit and redtape
>>> Intel (and others) had to jump around to get it included. Google has a
>>> lot of good karma in the llvm community and maybe that's the
>>> difference..
>>> _______________________________________________
>>> Openmp-dev mailing list
>>> Openmp-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
> _______________________________________________
> Openmp-dev mailing list
> Openmp-dev at lists.llvm.org
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