CGAL users discussion list

Philipp Moeller writes:
> Guillaume Damiand  writes:
> 
> > 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.
> 
> The allocator looks (minus the lacking rebind), conforming. From the
> errors it seems that In_place_list is at fault
> here. In_place_list_iterator has a converting constructor from T* (where
> T is the stored type), this won't work when the allocator defines
> pointer to by some smart-pointer type, which is the case for
> interprocess allocators. I have no idea if this is the only error, but
> there are likely to be more.

Thank you for all responses.
Could you please provide more info or any ideas how to make it working?
Maybe we could use something else than boost::interprocess::allocator which 
will be suitable in case of shared memory usage?