[GiNaC-list] multithreading

[Tony Worm]

from my understanding, the issue is with the memory system of  ginac
[anyone feel free to correct me on this]. It seems that ginac uses
reference counting is some form for ex types. In addition it seems
that they store the lookup in STL containers [map]. So when you try to
manipulate expressions from multiple threads, they are all trying to
access that lookup table. I imagine that it would be a rather
formidable task to alter the underlying memory system in ginac.

On Mon, Aug 23, 2010 at 12:23 PM, Cristobal Navarro <axischire at gmail.com> wrote:
> i understand the frustation :(
> i once opened a topic too, asking if a particular case would be thread
> safe,
> ginac is one of the best symbolic math libraries around, and it has proveed
> that it works great on large cluster problems, its just that the middle
> multithreading escenario is missing support, lets hope that in the future
> there could be plans for doing some work on the thread safety.
>
> On Mon, Aug 23, 2010 at 12:13 PM, Kraus Philipp <philipp.kraus at flashpixx.de>
> wrote:
>>
>> Am 23.08.2010 um 16:39 schrieb Cristobal Navarro:
>>
>>> in some cases,
>>> parallel symbolic algorithms obtain great performance increase, it all
>>> depends how you model the problem.
>>> im using ginac with openMPI to paralelize huge tree generators, i had to
>>> go the processes paralelism since multithread is not safe, but would be nice
>>> to be able to do that on the future
>>
>> I' working with MPI (on boost) and in this case it works on my test
>> system. But I would like to portage my algorithm without MPI support (on a
>> simple desktop system MPI support is not installed, but on these systems I
>> can use multithreading).
>> I have tried to compile ginac with -pthread on CXXFLAGS and the CLN
>> library. I analyse the compiled code with valgrind, you can show the
>> excerpt:
>>
>> ==51729== Possible data race during write of size 4 at 0x1ea4564 by thread
>> #3
>> ==51729==    at 0x3AB9: GiNaC::refcounted::add_reference() (in main)
>> ==51729==    by 0xF7C49F:
>> GiNaC::ptr<GiNaC::basic>::ptr(GiNaC::ptr<GiNaC::basic> const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C4B9:
>> GiNaC::ptr<GiNaC::basic>::ptr(GiNaC::ptr<GiNaC::basic> const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C4D3: GiNaC::ex::ex(GiNaC::ex const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C4ED: GiNaC::ex::ex(GiNaC::ex const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C51F: GiNaC::expair::expair(GiNaC::expair const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C539: GiNaC::expair::expair(GiNaC::expair const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7E4F3: void std::_Construct<GiNaC::expair,
>> GiNaC::expair>(GiNaC::expair*, GiNaC::expair const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>> ==51729==    by 0xF7F3E9: GiNaC::expair*
>> std::__uninitialized_copy_aux<__gnu_cxx::__normal_iterator<GiNaC::expair
>> const*, std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*>(__gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> __gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*, __false_type) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>> ==51729==    by 0xF7F43C: GiNaC::expair*
>> std::uninitialized_copy<__gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*>(__gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> __gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*) (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>> ==51729==    by 0xF7F45E: GiNaC::expair*
>> std::__uninitialized_copy_a<__gnu_cxx::__normal_iterator<GiNaC::expair
>> const*, std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*, GiNaC::expair>(__gnu_cxx::__normal_iterator<GiNaC::expair
>> const*, std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> __gnu_cxx::__normal_iterator<GiNaC::expair const*,
>> std::vector<GiNaC::expair, std::allocator<GiNaC::expair> > >,
>> GiNaC::expair*, std::allocator<GiNaC::expair>) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>> ==51729==    by 0xF7F518: std::vector<GiNaC::expair,
>> std::allocator<GiNaC::expair> >::vector(std::vector<GiNaC::expair,
>> std::allocator<GiNaC::expair> > const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>> in the same run:
>>
>> ==51729== Possible data race during read of size 4 at 0x1ea42f4 by thread
>> #3
>> ==51729==    at 0x3AB6: GiNaC::refcounted::add_reference() (in main)
>> ==51729==    by 0xF7C5AB: GiNaC::ptr<GiNaC::basic>::ptr(GiNaC::basic&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C5C5: GiNaC::ptr<GiNaC::basic>::ptr(GiNaC::basic&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C5ED: GiNaC::ex::ex() (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF7C604: GiNaC::ex::ex() (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xFCBC50: GiNaC::expairseq::expairseq() (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0x10BD804: GiNaC::mul::mul(GiNaC::ex const&, GiNaC::ex
>> const&) (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0x10BD88C: GiNaC::mul::mul(GiNaC::ex const&, GiNaC::ex
>> const&) (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0x10FF9D0: GiNaC::exminus(GiNaC::ex const&) (in
>> /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0x10FFDD0: GiNaC::operator-(GiNaC::ex const&, GiNaC::ex
>> const&) (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0x10BDB0C: GiNaC::mul::derivative(GiNaC::symbol const&)
>> const (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>> ==51729==    by 0xF965E3: GiNaC::basic::diff(GiNaC::symbol const&,
>> unsigned int) const (in /Developer/opt/Ginac/1.5.8/lib/libginac-1.5.0.dylib)
>>
>>
>> HTH the developers
>>
>> Phil
>>
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>
>
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