Hi,
You need to build MPIR in reentrant mode.
Also, you need to ensure that no two threads can write to the same MPIR
variable at the same time. It's just like writing any other parallel
program which uses data structures. There must be a separation of memory
regions used by the different threads. This is harder to do with OpenMP
than with pthreads directly.
Bill.
On 12 November 2015 at 11:07, <highcalcula...@gmail.com> wrote:
> Dear Bill, Dear All,
>
> after using MPIR successfully for some time, I am looking for a faster
> execution of my code and though of a parallel version. Is there a way to do
> it?
>
> I tried OpenMP by doing the following: In a toy example, I included
> <omp.h>, gcc’ed with "–fopenmp", and along the following non-MPIR code:
>
>
>
> int i, nloops, thread_id=0, N = 1000000;
>
>
>
> #pragma omp parallel private(thread_id, nloops)
>
>
> {
>
> nloops=0;
>
>
>
> #pragma omp for
>
> for (i=0; i<N; i++) {
>
> nloops++;
>
>
> }
>
> thread_id = omp_get_thread_num();
>
> printf("Thread %d performed %d iterations
> of the loop.\n", thread_id, nloops );
>
> }
>
>
>
> which resulted in the output:
>
> Thread 3 performed 250000 iterations of the loop.
>
> Thread 0 performed 250000 iterations of the loop.
>
> Thread 2 performed 250000 iterations of the loop.
>
> Thread 1 performed 250000 iterations of the loop.
>
>
>
> I then tried an MPIR version:
>
> int i, nloops, thread_id=0, N = 1000000;
>
> mpf_t a, b; mpf_inits(a, b, 0);
>
>
>
> #pragma omp parallel private(thread_id, nloops, a, b)
>
>
> {
>
> mpf_set_d(a, 0.0);
>
> mpf_set_d(b, 1.0);
>
>
>
> #pragma omp for
>
> for (i=0; i<N; i++) {
>
> mpf_add(a, a, b);
>
> }
>
> thread_id = omp_get_thread_num();
>
> gmp_printf("Thread %d performed %.*Ff
> iterations of the loop.\n", thread_id, 10, a );
>
> }
>
> mpf_clears(a, b, 0);
>
>
>
> which compiled without errors but resulted in an error (“program … stopped
> working during execution”) at runtime.
>
> Is it at all possible to run it in parallel with MPIR – and is there a
> mistake in the implementation?
>
> Tests: It runs through without error if the “mpf_add” inside the “#pragma
> for” loop is erased and b is set not after but before the “#pragma omp
> parallel” statement (but not if the “mpf_add” command is erased and b is
> declared as above).
>
> I am using gcc and MinGW on a 64-bit (2 cores) Windows 7 machine.
>
>
> Thanks and best regards!
>
>
>
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