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

Thu May 21 18:20:17 PDT 2020

On 5/21/20 2:37 PM, Churbanov, Andrey wrote:
> That may be a partial solution, but still there are problems.
>
> E.g. omp_display_env() does not have ident_t parameter, so if user would print _OPENMP macro and call omp_display_env() at the beginning, the library may not have a chance to get ident_t from compiler. If main program is compiled with -fopenmp then compiler can make internal call to runtime at the beginning, but otherwise printed version may depend on the sequence of OpenMP events in a program, - whether printing of version requested before or after runtime gets info from compiler.

Right, but we would need to actively set (potentially a lot) if we want 
it to be accurate all the time. What we could do instead is to print 
something like "5.0 or less" if we don't know (yet) and update it on a 
best effort basis. Results may vary if you mix things but they will not 
be totally bananas and we would indicate if we are "estimating".

> -- Andrey
>
> -----Original Message-----
> From: Johannes Doerfert <johannesdoerfert at gmail.com>
> Sent: Thursday, May 21, 2020 9:01 PM
> To: Churbanov, Andrey <Andrey.Churbanov at intel.com>; Joachim Protze <protze.joachim at gmail.com>; Wilmarth, Terry L <terry.l.wilmarth at intel.com>; Jonas Hahnfeld <hahnjo at hahnjo.de>
> Cc: openmp-dev at lists.llvm.org
> Subject: Re: [Openmp-dev] Removing spec versioning from the OpenMP runtime
>
>
> On 5/21/20 12:51 PM, Churbanov, Andrey wrote:
>> What if the code was compiled my multiple compilers?
>> User can link objects compiled by gcc5, gcc9, clang9, clang10, clang11, icc19, icc19.1, etc. into a single application. Supported version in different objects may not match of cause.
>
> Wouldn't my solution take care of that (in the future)?
>
> If there is no OpenMP version in the ident_t struct we say we don't know/are guessing/unsure or something similar.
>
>
>> -- Andrey
>>
>> -----Original Message-----
>> From: Openmp-dev <openmp-dev-bounces at lists.llvm.org> On Behalf Of Johannes Doerfert via Openmp-dev
>> Sent: Thursday, May 21, 2020 8:28 PM
>> To: Joachim Protze <protze.joachim at gmail.com>; Wilmarth, Terry L <terry.l.wilmarth at intel.com>; Jonas Hahnfeld <hahnjo at hahnjo.de>
>> 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
>>
>>
>> On 5/21/20 12:04 PM, Joachim Protze via Openmp-dev wrote:
>>> 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?
>> We could encode it in the ident_t which should also solve the issue
>>
>> with mixing openmp versions during compile time.
>>
>>
>>
>>> 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
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
>>>> _______________________________________________
>>>> Openmp-dev mailing list
>>>> Openmp-dev at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
>>>>
>>> _______________________________________________
>>> Openmp-dev mailing list
>>> Openmp-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
>> _______________________________________________
>> Openmp-dev mailing list
>> Openmp-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/openmp-dev
>>
>> --------------------------------------------------------------------
>> Joint Stock Company Intel A/O
>> Registered legal address: Krylatsky Hills Business Park,
>> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
>> Russian Federation
>>
>> This e-mail and any attachments may contain confidential material for
>> the sole use of the intended recipient(s). Any review or distribution
>> by others is strictly prohibited. If you are not the intended
>> recipient, please contact the sender and delete all copies.
> --------------------------------------------------------------------
> Joint Stock Company Intel A/O
> Registered legal address: Krylatsky Hills Business Park,
> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
> Russian Federation
>
> This e-mail and any attachments may contain confidential material for
> the sole use of the intended recipient(s). Any review or distribution
> by others is strictly prohibited. If you are not the intended
> recipient, please contact the sender and delete all copies.