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[asio] Feature request for serializable types.
by Germán Diago 22 Aug '10

22 Aug '10

Hello. I'm using boost.asio and trying to serialize a boost.variant, which is serializable because each of the fields I used in the variant have a serialize method required by boost.serialization library. I want to send my variant as binary data. This is not easy although I have a serialize method because this does not work: async_write(mysocket, boost::asio::buffer(myserializablevariant), when_done); I think all serializable types should be automatically usable as boost::asio::buffer, like std::vector, in this call. I think this shouldn't be too hard to implement, but I don't know how to serialize my data in binary format in a straight-forward way. Any ideas? Thanks in advance.

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thread-safe initialization for singleton
by Kraus Philipp 22 Aug '10

22 Aug '10

Hi, I have written a class with static methods and properties. Now the class must be used in a multithreaded environment, so I get some race conditions error. I use boost::thread for implementating the threads. I have found boost_once but I don't know how to use it, so my class properties are initialized once. Thanks Phil

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multiple serialized objects to same file
by Oscar Pernas 21 Aug '10

21 Aug '10

Hi! I know that this question is asked before but I cant see any answer about it. Is posible with boost serialization to write different objects to the same file? if is possible, is possible to access to each object with an iterator or with position like binary files? thanks -- Óscar Pernas Plaza.

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[BGL] segFault
by John Robertson 21 Aug '10

21 Aug '10

I'm trying to obtain an iterator of edges with a different ordering than that given in egdes(g). The following compiles but segfaults at std::sort( VE.begin(), VE.end(), ordering< Graph, edd >() ); (runs ok if the above line is commented out) //////////////////////////////////////////////////////////////////////////////////////////////////////////////// typedef Traits::edge_descriptor edd; // Create ordering template < typename Graph, typename edd > struct ordering { Graph & g; bool operator ()(const edd & a, const edd & b) { return g[a].eName < g[b].eName; } }; template < typename Graph > int initialize_container( Graph & g ) { typename graph_traits<Graph>::edge_iterator edge_iter, edges_end; // create vector of edge descriptors. std::vector< Traits::edge_descriptor > VE(num_edges(g)+1); int i = 1; // (Sometimes I like to start at 1.) //insert edge descriptors into vector of edge descriptors. for (tie(edge_iter, edges_end) = edges(g); edge_iter != edges_end; ++edge_iter) { cout << " *edge_iter = " << *edge_iter << endl; VE[i++] = *edge_iter; } // segfaults here //sort vector of edge descriptors. std::sort( VE.begin(), VE.end(), ordering< Graph, edd >() ); //print sorted edge descriptors. for( int i = 1; i < num_edges(g)+1; ++i ) cout << " -Edge " << i << " = " << VE[i] << endl; } Thanks

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[BGL] Updating the source vertex of an edge in-place
by Daniel Trebbien 21 Aug '10

21 Aug '10

I need to be able to update the source vertex of an edge in-place. The only option that I see is to remove the edge with `remove_edge` and then add a new edge with `add_edge`. The problem, however, is that I think this will mess up a property map of an edge property if it cannot expand to map a new value for the newly-added edge. Thus, I would like to update the edge in-place. How do I do this?

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[propertytree] more beginners questions
by Dietmar Hummel 21 Aug '10

21 Aug '10

Hi! I have some more questions regarding property tree (for parsing xml) and maybe someone could help me. Lets assume we have the following xml file to read: <a> <b> <c><d>1</d></c> <c><d>2</d></c> <c><d>3</d></c> <x></x> </b> </a> Now, my idea was to parse all the c-nodes by calling a specific function for each of them. Something like this... void parseDNode( const boost::property_tree::ptree& v ) { //... } void parseCNode( const boost::property_tree::ptree::value_type& v ) { parseDNode( v.second.get_child( "d" ) ); } void load( const std::string& filename ) { boost::property_tree::ptree pt; boost::property_tree::read_xml(filename, pt); BOOST_FOREACH( boost::property_tree::ptree::value_type &v, pt.get_child( "a.b.c" ) ) { parseCNode( v ); } } ---- Now I have several questions for this: 1. The code doesn't work as expected, it just handles the first one of the c nodes 2. The function parseCNode() also doesn't work. I assumed that v is a reference to the c node where I have to claim the d-node by get_child. But it seems v is already pointing to d? 3. I don't understand why BOOST_FOREACH is working with value_type here. As far as I see, get_child returns a self_type which should be a ptree? See also the different parameter lists for parseCNode and parseDNode... Thanks in advance.... Regards Dietmar

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MPICH2 + Boost.MPI Collective Problems
by Stephan Hackstedt 21 Aug '10

21 Aug '10

Hi there, i have a big problem by running MPI programs which use the Boost.MPI library. When i'm trying to run programs on *more *than one node, collective operations like communicator::barrier<http://boost.org/doc/libs/1_44_0/doc/html/boost/mpi/communicator.html#id918…>or broadcast,<http://boost.org/doc/libs/1_44_0/doc/html/boost/mpi/broadcast.html>or even the environment<http://boost.org/doc/libs/1_44_0/doc/html/boost/mpi/environment.html>destructor (cause of FINALIZE, which is colletive) causing the programm to crash. I got errors like this : *[1]terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::mpi::exception> >' [1] what(): MPI_Barrier: Other MPI error, error stack: [1]PMPI_Barrier(362).................: MPI_Barrier(MPI_COMM_WORLD) failed [1]MPIR_Barrier_impl(255)............: [1]MPIR_Barrier_intra(79)............: [1]MPIC_Sendrecv(186)................: [1]MPIC_Wait(534)....................: [1]MPIDI_CH3I_Progress(184)..........: [1]MPID_nem_mpich2_blocking_recv(895): [1]MPID_nem_tcp_connpoll(1746).......: Communication error with rank 0: * I also tested this with the simple broadcast example from the Boost.MPI tutorial - same errors.. But when using the original MPI equivalent without the Boost.MPI library, such as MPI_Barrier<http://www.mpi-forum.org/docs/mpi-11-html/node66.html#Node66>, the programm runs well. I am using MPICH2 on Ubuntu 10.04 platforms. Someone had problems like this or know a fix for that? Regards, stephan

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Using unordered_set or unordered_map to hold small array(s) of ints
by B Hart 21 Aug '10

21 Aug '10

Can someone please provide an example of how to best use unordered_map/set to store/lookup many small arrays of integers. e.g. unsigned int I[5] = {1000,3344455,12455222,8832232}; I'm guessing that there is no facility for using raw C++ arrays, and that one must wrap them in a struct. Thanks in advance.

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Beginner question: Why boost::signal creates another instance of the slot object ?
by Mauricio Gomes 20 Aug '10

20 Aug '10

Hi, I am running the program below (Vista with boost 1.43, mingw/gcc 4.5.1). I would expect slot.x to be 5 but it is zero. Why boost::signal creates another instance of the slot object ? What am I missing here ? Thank you in advance for your attention, Mau. ---------------------------------------------------------------- #include <iostream> #include <boost/signal.hpp> struct S { int x; S (): x(0) {} void operator () (int i) { std::cout << "&slot1 = " << this << std::endl; x = i; std::cout << "slot1.x = " << this->x << std::endl; } }; int main () { S slot; boost::signal<void (int)> sig; std::cout << "&slot2 = " << &slot << std::endl; sig.connect (slot); sig (5); std::cout << "slot2.x = " << slot.x << std::endl; return 0; } -------------------------------------------------------------------- Output: &slot2 = 0x22fee4 &slot1 = 0x341448 slot1.x = 5 slot2.x = 0

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How to best use unordered_set or unordered_map to hold small array(s) of ints
by B Hart 20 Aug '10

20 Aug '10

I posted this last night, but not sure it went through to the list as I don't see it in my sent items and I never got any responses. Sorry if it is duplicate. I'm hoping someone could offer an example or advice on how to best use unordered_set or unordered_map to hold many small arrays of unsigned integers. I would like to use the built in hash function rather than have to create one. Also, since I have many of these small arrays, keeping the memory footprint small and the hash time at a minimum are important concerns. A typical int array would hold 5 unsigned ints. Maybe someone could offer example code or suggestions. The samples I see are always the trivial case of just entering a single number or string as key or value. Thanks.

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