[Openmp-dev] KMP_GOMP_COMPAT now required?

[Finkel, Hal J.]

I think that the build system is okay, I was just experimenting, trying to understand what the various preprocessor macros do.

Thanks again,
Hal

Sent from my Verizon Wireless 4G LTE DROID


"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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