Hi Martin, ISO 14882:2003 (the C++03) standard doesn't clearly specify how containers must swap its contents. It's clearly specified in C++0x drafts. Most implementations simply exchange internal block (pointers) and capacity, if allocators are the same. Otherwise, each element will be copied.
ref_ptr can be easily used in either case (latter case being the inefficient/different allocator case), because it satisfies the requirements (from C++03): 25.2.2 Swap [lib.alg.swap] template<class T> void swap(T& a, T& b); 1 Requires: Type T is CopyConstructible (20.1.3) and Assignable (23.1). 2 Effects: Exchanges values stored in two locations. ref_ptr<T> is CopyConstructible and Assignable; its copies are equivalent. Ismail On Wed, Apr 15, 2009 at 5:10 PM, Martin Beckett <m...@mgbeckett.com> wrote: > vector typically doubles the size of memory it reserves when it needs more > space. This is because every time it allocates new memory it must move the > contents of the existing memory - it's slow to copy all the existing elements > and so it makes sense to only increase as few times as possible (see > http://www.ddj.com/cpp/184401375 for a discussion). > Unfortunately this isn't a good stratergy when you are almost out of memory. > > Another problem is that the memory must be contiguous (ie in one block), so > if you frequently allocate and delete memory there might not be a single free > block large enough - even if you have enough overall memory. > > There is also a little 'trick' to reduce a vector back down to the minimum > required memory - see http://www.gotw.ca/gotw/054.htm > > Code: > vector<stuff>( c ).swap( c ); > > > > (note - can someone confirm the swap() trick works with ref counting?) > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=10259#10259 > > > > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
