CGAL users discussion list

[Guillaume Damiand <>]

Hi,


Le 25/10/2012 13:15, Pawe? P. a écrit :
> Hi!,
>
> I am taking part in the development of project focused on creating high
> performance data processing environment in C++ / C++11 right now on linux (but
> we are planning to add other platforms in the future). Right now me and my
> team are doing research in field of 3D graphics data structures.
>
> As one of our options we are concidering CGAL as library, on which we will
> base.
>
> During the research we came across a big problem with allocating
> CGAL::Polyhedron_3 on shared memory. We have searched the web for answer,
> asked several questions mainly on stackoverflow, but so far, we've got no real
> solution.
>
> As short overwiew – we want to implement a mechanism allowing for sharing 3D
> data structures between applications. Of course it is possible to stream
> geometry to OFF format to shared memory from source application and then
> stream it back in target application (like in
> http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Polyhedron/Chapter_main.html#Subsection_25.3.6),
> but it is to slow for our purpose (double conversion) and we want to be able
> to operate on CGAL's geometry inside shared memory, in such way, that
> independend applications could use it as is.
>
> Please take a look at these questions:
> http://stackoverflow.com/questions/12657030/share-cgals-geometry-between-processes-in-c
> http://stackoverflow.com/questions/12807616/how-to-allocate-cgals-halfedge-struture-in-shared-memory
>
> We know, that according to the CGAL's documentation
> (http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Polyhedron_ref/Class_Polyhedron_3.html#Cross_link_anchor_1110)
> the allocators should be as follow:
>
> “The fourth parameter Alloc requires a standard allocator for STL container
> classes.”.
>
> The problem is that it is impossible to use std::allocator on shared memory.
>
> We were trying to use boost::interprocess::allocator as Polyhedron_3
> allocator, but we have found out that we need stateless allocator like
> std::allocator (becouse during initialization of Polyhedron_3 there is no way
> to pass arguments to constructor of custom, non stateless allocator). We have
> also implemented very simple class extending boost::interprocess::allocator to
> make it stateless (code sample: http://pastebin.com/uJYG6AP4) The problem is
> that it's working with other objects like vector but not with Polyhedron_3 (it
> gives some complex compilation errors).
>
> We would be very gratefull for any tips/solutions in this matter.

I think you need to modify your MyBoostAllocator class to satisfy all 
the requirements of the std::allocator concept.

I tested your code using another allocator (cf [1]) and it works.

Guillaume

[1] 
http://www.codeguru.com/cpp/cpp/cpp_mfc/stl/article.php/c4079/Allocators-STL.htm



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Guillaume DAMIAND

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