[Openmp-dev] KMP_GOMP_COMPAT now required?

[Steven Noonan]

Curious, wouldn't it make more sense to default to sensible behavior
and require macro definitions for the exceptional cases? In what
circumstances would you not want KMP_GOMP_COMPAT set?

On Mon, Mar 17, 2014 at 6:59 AM, Cownie, James H
<james.h.cownie at intel.com> wrote:
> KMP_GOMP_COMPAT has always been required. That is the intent.
> If KMP_GOMP_COMPAT is not being set automatically by the build system then that has got broken somewhere. (Maybe one of Alp's recent changes broke this unintentionally?)
>
> -- Jim
>
> James Cownie <james.h.cownie at intel.com>
> SSG/DPD/TCAR (Technical Computing, Analyzers and Runtimes)
> Tel: +44 117 9071438
>
>
> -----Original Message-----
> From: openmp-dev-bounces at cs.uiuc.edu [mailto:openmp-dev-bounces at cs.uiuc.edu] On Behalf Of Hal Finkel
> Sent: Monday, March 17, 2014 1:15 PM
> To: openmp-dev
> Subject: [Openmp-dev] KMP_GOMP_COMPAT now required?
>
> Hello,
>
> I've noticed that KMP_GOMP_COMPAT is now required? Is this the intended behavior?
>
> Specifically, because of this in kmp_ftn_entry.h:
>
> /*
>  * For compatibility with the Gnu/MS Open MP codegen, omp_set_num_threads(),
>  * omp_set_nested(), and omp_set_dynamic() [in lowercase on MS, and w/o
>  * a trailing underscore on Linux* OS] take call by value integer arguments.
>  * + omp_set_max_active_levels()
>  * + omp_set_schedule()
>  *
>  * For backward compatibility with 9.1 and previous Intel compiler, these
>  * entry points take call by reference integer arguments.
>  */
> #ifdef KMP_GOMP_COMPAT
> # if (KMP_FTN_ENTRIES == KMP_FTN_PLAIN) || (KMP_FTN_ENTRIES == KMP_FTN_UPPER) #  define PASS_ARGS_BY_VALUE 1 # endif #endif #if KMP_OS_WINDOWS # if (KMP_FTN_ENTRIES == KMP_FTN_PLAIN) || (KMP_FTN_ENTRIES == KMP_FTN_APPEND) #  define PASS_ARGS_BY_VALUE 1 # endif #endif
>
> As a result, if KMP_GOMP_COMPAT is not defined, and we're not on Windows, the omp_set_num_threads expects its argument by reference. This is incompatible with its signature (and the standard):
>
>   omp_set_num_threads (int);
>
> and obviously attempting to dereference the argument will segfault.
>
> Would it make more sense to define a special build flag for Intel 9.1 compatibility, and otherwise do the expected thing and expect these arguments by value?
>
> Thanks again,
> Hal
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
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