How to clear unknown pragma warning for OpenMP?

Jeffrey Walton noloader@gmail.com
Thu Jul 23 18:19:00 GMT 2015


> You might be able to use _Pragma
>
> #if _OPENMP
> #define OMP_PARALLEL _Pragma("omp parallel")
> #else
> #define OMP_PARALLEL
> #endif
>
> And then use that instead of the #pragma omp directive:
>
>   OMP_PARALLEL
>   for (int i = 0; i < 10; ++i)
>     ;

Yeah, that crossed my mind. I realized I was attacking the defines
from the wrong end.

> Again, I haven't actually tested whether this still parallelizes
> anything, only that it compiles.

It gets even better: benchmarking, I found some of the routines slowed
down. Hence the reason for that weird looking tail on the pragma:


    #pragma omp parallel sections if(CRYPTOPP_RW_USE_OMP)
    {
        #pragma omp section
            m_pre_2_9p = modp.Exponentiate(2, (9 * m_p - 11)/8);
        #pragma omp section
            m_pre_2_3q = modq.Exponentiate(2, (3 * m_q - 5)/8);
        #pragma omp section
            m_pre_q_p = modp.Exponentiate(m_q, m_p - 2);
    }

(The 'if' clause has been around since OMP 1.0, so its available everywhere).

Jeff



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