[Openmp-dev] Removing spec versioning from the OpenMP runtime

[Joachim Protze via Openmp-dev]

Hi all,

sorry for necromancing on this thread :D

I came across this issue, when working on an OMPT example for the OpenMP 
Examples document. Currently, the runtime would print _OPENMP='201611', 
when exporting OMP_DISPLAY_ENV=1.
This is other than the value of _OPENMP=201511 during compilation. 
Furthermore, 201611 is not a value defined in any spec.

I had a discussion about OpenMP versions with Michael Klemm (OpenMP CEO 
/ Intel) a while ago. From his perspective OpenMP compiler and runtime 
should always be seen as one paired thing.
So, if the compiler supports and exposes different behavior for 
different OpenMP versions, the runtime should be aware of that.

So, if we try to implement differently specified behavior (as suggested 
by -fopenmp-version=51), the proper thing to do from my perspective 
would be to pass on the compile time version to the runtime.
The runtime then "could" do specific things at execution time. At least, 
the runtime would print out the right version string for OMP_DISPLAY_ENV=1.

What do you think about this? How can we make this work?

Best
Joachim


Am 14.02.19 um 21:02 schrieb Wilmarth, Terry L via Openmp-dev:
> Since there are no objections to this, we'll start on it soon.
> Thanks for the feedback!
> 
> -----Original Message-----
> From: Jonas Hahnfeld [mailto:hahnjo at hahnjo.de]
> Sent: Thursday, February 7, 2019 1:39 AM
> To: Wilmarth, Terry L <terry.l.wilmarth at intel.com>
> Cc: LLVM-OpenMP (openmp-dev at lists.llvm.org) <openmp-dev at lists.llvm.org>
> Subject: Re: [Openmp-dev] Removing spec versioning from the OpenMP runtime
> 
> Hi Terry,
> 
> I'm in favor as suggested in https://reviews.llvm.org/D55496.
> To add another argument that was raised in that review: Currently the tests need to be versioned as well, which is another maintenance burden.
> 
> Cheers,
> Jonas
> 
> On 2019-02-06 20:13, Wilmarth, Terry L via Openmp-dev wrote:
>> Hello,
>>
>> We're considering removing all of the spec versioning in the runtime.
>> This is the set of spec-version-numbered #ifdefs throughout the
>> runtime (such as OMP_40_ENABLED, OMP_45_ENABLED, OMP_50_ENABLED, etc.)
>> that make it possible to build earlier versions of the runtime that
>> are compliant with a certain spec version, via LIBOMP_OMP_VERSION.
>>
>> The main reasons to remove this:
>>
>> 1)      No one seems to be using the spec-version builds.
>>
>> 2)      The #ifdefs are often not well-maintained or correctly added.
>>
>> 3)      The #ifdefs add clutter to the source.
>>
>> We'd like to get some feedback on removing this.  If we're generally
>> in agreement that it should be removed, we'll start work on the
>> cleanup.
>>
>> Thanks!
>>
>> Terry
>>
>> Terry L. Wilmarth
>> terry.l.wilmarth at intel.com   512-362-0530
>> Intel/Threading Runtimes
>> _______________________________________________
>> Openmp-dev mailing list
>> Openmp-dev at lists.llvm.org
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