Sure Ion, thanks for answering. Commenting or uncommenting the last line (the one with insert) you get the compilation error. I don?t know how to insert something into the multimap... Thanks in advance (I tried to follow the code behind flat_tree but got confused as I think a std::pair is what's expected??) --------------- #include <vector> #include <boost/shmem/named_shared_object.hpp> #include <boost/shmem/containers/string.hpp> #include <boost/shmem/containers/flat_set.hpp> #include <boost/shmem/containers/flat_map.hpp> #include <boost/shmem/allocators/allocator.hpp> #include <boost/shmem/offset_ptr.hpp> #include <boost/functional/hash.hpp> #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> class myShmNode { //whatever }; typedef boost::shmem::allocator<myShmNode *, boost::shmem::named_shared_object::segment_manager> myShmNodePtrAllocator; typedef boost::shmem::flat_multimap<size_t, myShmNode*, std::less<myShmNode*>, myShmNodePtrAllocator> MyMultiMap; int main(int argc, char *argv[]) { boost::shmem::named_shared_object segment; segment.create( "/MySharedMemory", 1048576 ); //Initialize shared memory STL-compatible allocators myShmNodePtrAllocator nodesPtrsAllocator(segment.get_segment_manager()); std::less<myShmNode*> comparator2; MyMultiMap* ptrsMultiMap=segment.construct<MyMultiMap>(boost::shmem::anonymous_instance) (comparator2,nodesPtrsAllocator); typedef std::pair<size_t,myShmNode*> multiMapNodeType; multiMapNodeType multiMapNode; myShmNode* myNode; multiMapNode.first = 1; multiMapNode.second = myNode; ptrsMultiMap->insert(multiMapNode); }