On 31/12/2017 17:33, Thomas LE MÉZO wrote:
Dear Enea, Dear all,
I tried recently to implement a multi-thread version of my thesis code using PPL library. I used OpenMP and the last version of ppl on devel git branch as I read you have been working on a thread-safe implementation (thread-safe option with configure). I didn't succeed in writing a correct program; see for instance this simple code that return a segmentation fault :
#include <omp.h>
namespace PPL = Parma_Polyhedra_Library;
int main(){
#pragma omp parallel for for(int i=0; i<1000; i++){ PPL::C_Polyhedron ph1(3); // => segmentation fault at line 83 of Linear_Expression.cc PPL::C_Polyhedron ph2(3); ph1.intersection_assign(ph2); } return 0; }
Would you have any idea about what is wrong?
Each thread should be properly initialized by creating a PPL::Thread_Init object (and finalized by destroying it). See for instance test01() in tests/Polyhedron/threadsafe1.cc As an alternative, you could use the make_threadable wrapper (see test02() in the same test).
Is PPL compatible with using OpenMP?
I never tried using it with OpenMP ... however, as long as thread initializations (and finalizations) are performed as suggested above, things should be working (there is also a library initialization part, but that is automatically done when working in C++).
In you code, I would try adding
PPL::Thread_Init thread_init;
as the very first line of the loop body. This would maybe create more init objects than needed, but (if I remember correctly) that should not be a problem.
Let us know how it goes.
Enea
Thanks a lot in advance,
Thomas
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