Ok; how can I build it in re-entrant mode and check whether I might have
done so already (since the successful build took a long time...)?
Regarding the separation of memory regions: What is wrong with the
following code:
int i, N = 10;
mpf_t a[N], b;
for (i=0; i<N; i++) { mpf_init(a[i]); }
mpf_init(b);
#pragma omp parallel private(a, b)
{
for (i=0; i<N; i++) { mpf_set_d(a[i], (double) i); }
mpf_set_d(b, 1.0);
#pragma omp for
for (i=0; i<N; i++) {
mpf_add(a[i], a[i], b);
}
}
which again lets the program crash at runtime only.
And where is a good introduction to using pthreads?
Thanks a lot.
On Thursday, November 12, 2015 at 11:22:46 AM UTC+1, Bill Hart wrote:
>
> 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, <highcal...@gmail.com <javascript:>> 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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>
>
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