Hi Berenguer, flat_map has the same interface as map so if you have more problems, try to make an small example using map. Regarding flat_xxx family: The comparison function must compare keys, not mapped types: std::less<size_t> The allocator must allocate pairs: allocator <std::pair<size_t, myShmNode*>, segment_manager> if you were using boost::shmem::map the stored objects are const keys so you would need allocator <std::pair<const size_t, myShmNode*>, segment_manager> This is your modified example. Compiles fine in Visual 7.1. I left commented the code I've changed: #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 <std::pair<std::size_t, myShmNode *>/*myShmNode **/ ,boost::shmem::named_shared_object::segment_manager> myShmNodePtrAllocator; typedef boost::shmem::flat_multimap <size_t ,myShmNode* ,std::less<std::size_t/*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<std::size_t/*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); }