September 2012 - Boost-users - lists.preview.boost.org

chaining functions input output
by MM 19 Feb '13

19 Feb '13

Hello, i have these 2 functions provided to me and I wonder whether they can somehow be chained without using intermediary memory? http://codepad.org/tTwkUQhp Rds, MM

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[Program Options] terminate parsing after first positional argument
by Stuart Pook 22 Jan '13

22 Jan '13

Hello, How can I tell Boost Program Options to stop parsing the arguments as soon as it finds a positional argument? I'd like to be able to parse the argument list "-v chmod -R -v 600 foo" as having one argument for my program (-v) and the rest as a std::vector of std::string (including the -v). In the attached program I have tried 2 different approaches. The first uses multitoken with the arguments "--command date -u -v", it fails because "-u" isn't known. The second uses collect_unrecognized with "chmod -R -v 600", it doesn't work because -v is interpreted by boost and doesn't end up in the vector. As someone said back in 2005, perhaps I'm trying to write xargs: http://thread.gmane.org/gmane.comp.lib.boost.user/9529/focus=9641 I know that I can ask my users to write a.out -v -- chmod -R -v 600 foo but I don't want to do that. I want them to write "a.out -v chmod -R -v 600 foo". The first positional argument should should tell boost to stop processing. Another slightly different question. If I have a multitoken option that takes doubles how can I get it to accept negative values? If I give my program "--floats 1 8 -4 6" where --floats starts a multitoken option that accepts double, I get an exception saying that "-4" is an unknown option. thanks Stuart This is what my test program gives me with boost 1.50: argv: dd --command date -u -v unrecognised option '-u' Allowed options: -v [ --verbose ] verbose --command arg command to run 2nd try argv: dd chmod -R -v 600 I'm verbose v: chmod -R 600 3rd try argv: dd --floats 1 8 -4 6 unrecognised option '-4' Allowed options: -v [ --verbose ] verbose -f [ --floats ] arg numbers and my program (formatted to fit in 80 characters) #include <boost/program_options.hpp> #include <boost/range/algorithm.hpp> #include <boost/program_options/parsers.hpp> #include <boost/program_options/options_description.hpp> #include <iostream> namespace po = boost::program_options; #define nelements(a) (sizeof (a) / sizeof (a)[0]) void print(char const * * b, char const * * e) { std::cout << "argv: "; std::copy(b, e, std::ostream_iterator<char const *>(std::cout, " ")); std::cout << std::endl; } int main(int argc, char ** argv) { { bool verbose; std::vector<std::string> command; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("command", po::value<std::vector<std::string> >(&command) ->multitoken(), "command to run") ; char const * args[] = { "dd", "--command", "date", "-u", "-v", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(desc).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "command: "; boost::copy(command, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; } } std::cout << "2nd try\n"; { bool verbose; po::options_description desc("Allowed options"); desc.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ; char const * args[] = { "dd", "chmod", "-R", "-v", "600", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; po::parsed_options parsed = po::command_line_parser(nelements(args) - 1, args). options(desc).allow_unregistered().run(); try { po::store(parsed, vm); } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << desc << "\n"; exit(2); } po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "v: "; std::vector<std::string> v = po::collect_unrecognized( parsed.options, po::include_positional); boost::copy(v, std::ostream_iterator<std::string>(std::cout, " ")); std::cout << std::endl; } std::cout << "3rd try\n"; { bool verbose; std::vector<double> f; po::options_description all("Allowed options"); all.add_options() ("verbose,v", po::bool_switch(&verbose)->default_value(false), "verbose") ("floats,f", po::value<std::vector<double> >(&f)->multitoken(), "numbers") ; char const * args[] = { "dd", "--floats", "1", "8", "-4", "6", 0 }; print(args, args + nelements(args) - 1); po::variables_map vm; try { po::store(po::command_line_parser(nelements(args) - 1, args) .options(all).run(), vm); po::notify(vm); if (verbose) std::cout << "I'm verbose\n"; std::cout << "floats: "; boost::copy(f, std::ostream_iterator<double>(std::cout, " ")); std::cout << std::endl; } catch (boost::program_options::unknown_option & x) { std::cerr << x.what() << "\n" << all << "\n"; } } }

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[mpi] many undefined references to serialize<boost::mpi::detail::mpi_datatype_oarchive>
by Brian Budge 30 Oct '12

30 Oct '12

Hi all - I've got a class hierarchy that can already be serialized into text or binary archives. I'm explicitly instantiating the template functions for serialize and/or load/save. I'm trying to add the capability to have boost mpi perform the serialization through send/recv/broadcast. I've added explicit instantiations for the boost::mpi::packed_iarchive and packed_oarchive. My code compiles, but at the end I get a bunch of undefined references for serialize<boost::mpi::detail::mpi_datatype_oarchive>. I can add the explicit instantiations for this oarchive, and this seems to fix my linking issue, but this seems broken, i.e. I should not have to deal with anything in a boost::detail namespace? Is there another suggestion for how to get this to work? Thanks, Brian

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[units] Missing quantity operator++, operator%
by Nathan Crookston 25 Oct '12

25 Oct '12

All, I'm in the process of switching my homegrown units system over to boost units. Some operators which I'm missing are the modulus and the pre and post increment operators. Looking through the archives I note an original review[1] which mentioned the absence of those operators. One response claimed that quantity<si::length, int> t = 5. ...; t++; was nonsensical as writing 5 m + 1, and the reviewer eventually agreed, citing possible confusion if the quantity type converted the initializer. Matthias Schabel seemed to respond favorably: 'I debated this for a while - the only problem is that there will be some value types with heterogeneous operator+ / operator- for which q + 1 is not the same type as q, but I guess that it is just OK for it to just give a compile error in those cases.' And Steven Watanabe said 'Will do.' I haven't found anything regarding the modulus operator. My question is, would a patch adding those operators be accepted? Thanks, Nate [1] http://lists.boost.org/Archives/boost/2007/03/119001.php

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[fusion] making an inner struct boost fusion compatible?
by Oswin Krause 17 Oct '12

17 Oct '12

Hi list, I have the following problem: template<class T, class U, class V> struct MyType{ struct nested{ typename MetaFunc<T>::type a; typename MetaFunc<U>::type b; typename MetaFunc<V>::type c; }; }; now this inner struct must be a boost fusion compatible random access sequence. The examples cover only structs on namespace lvel, how can i handle this way? Later these classes will be generated by a macro automatically so even dirty hacks are allowed :). But i don't want to clatter the namespace by pulling nested outside of the class. Is there an easy way or do i have to write the necessary mtafunctions to make this possible? Greetings, Oswin

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Asio and ZeroMQ
by Matthias Vallentin 11 Oct '12

11 Oct '12

A while ago, Maciej Gajewski started an effort to use Asio to observe a ZeroMQ socket [1]. Based on his code, I put together a thin library that wraps the implementation details. Since other have requested a working example, here it is now at github: https://github.com/mavam/bmq Any feedback is highly appreciated. A basic usage example looks like this: #include <boost/asio/io_service.hpp> #include <bmq.h> int main() { boost::asio::io_service io; bmq::context ctx(1); bmq::component c(ctx, io); auto sink = c.add_sink(ZMQ_PAIR, "inproc://x"); c.subscribe(sink, [](bmq::message&& msg) { std::string str(static_cast<char*>(msg.data()), msg.size()); std::cout << str << std::endl; }); auto source = c.add_source(ZMQ_PAIR, "inproc://x"); bmq::message msg(const_cast<char*>("foo"), 3, nullptr); source->send(msg); // Execute message handler. io.poll(); return 0; } At this point, the library is really thin and only provides very rudimentary wrapping of ZeroMQ. In the future, I plan to extend it in order to facilitate applications that build on message-passing. The dataflow abstraction I envision is essentially a directed graph, where nodes represent components and edges communication links. 0mq provides the edges and the Asio handles asynchronous event processing at the component level. The motiviation is that this model lends itself well for scaling out distributed systems over large clusters. Matthias [1] http://permalink.gmane.org/gmane.network.zeromq.devel/9538

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CSR graph and Dijkstra's to lower graph memory
by jer.k 08 Oct '12

08 Oct '12

Hello, This is my first post and I'm very new to BOOST, so please let me know if I have missed some of the mailing list etiquette :) When I run Dijkstra's on my graph, I quickly run out of memory and I'm trying to find ways to lower the memory needed to store the graph. My graphs has around ~3,600,000 nodes and ~580,000,000 edges (I will eventually need a graph at least 5x this number - more if possible). I only store a weight (double) at each edge (I don't need to store any information at each node) and find that while this only takes about 1.5 hrs to run, this takes up around ~95GB (I have access to a cluster so I can run these high memory jobs). I use an adjacency_list to store this graph. typedef adjacency_list < setS, vecS, undirectedS, no_property, property < edge_weight_t, double > > graph_t; My two questions are: 1) Is this a reasonable amount of memory to expect a graph of this size using an adjacency_list? Or am I doing some terribly wrong? This is much more memory needed than I expected. 2) From what I understand, the compressed sparse row (CSR) graph is a possible solution to lowering the memory requirements as I know the number of edges and the number of nodes prior to forming the graph. I've been going through the documentation and I followed this tread <http://boost.2283326.n4.nabble.com/Graph-On-Dijkstra-SSSP-performance-td444…> which had an example of using a CSR instead of an adjacency_list and running Dijkstra's. However I can't seem to get the last step (last reply by Jeremiah Willcock) of > "plus adding the weight map parameter explicitly > to the call to dijkstra_shortest_paths_no_color_map" to work successfully. I guess I'm not sure how to add the weigh map parameter to the Dijkstra's call. The following is the relevant code dealing with edge weights. ======= ... struct Edge_Cost { double weight;}; // Needed for bundled properties. Edge_Cost *edgeCosts = new Edge_Cost[2]; // Add 3 edges costs. edgeCosts[0].weight = (2.0); edgeCosts[1].weight = (5.2); edgeCosts[2].weight =(3.33); ... typedef compressed_sparse_row_graph<directedS, WebPage, // From the example docs on CSR Edge_Cost // The struct. > graph_t; graph_t g(boost::edges_are_unsorted, &the_edges[0], &the_edges[0] + numEdges, edgeCosts, // Add the weights here??? numNodes); ... boost::dijkstra_shortest_paths(g, // The graph. s, // VertexDescriptor - the source vertex. &p[0], &d[0], edgeCosts, // <--- WHAT DO I PUT HERE?? indexmap, std::less<int>(), closed_plus<int>(), (std::numeric_limits<int>::max)(), 0, default_dijkstra_visitor() ); ======= When I run this, I get several errors, the first is: error C2664: 'boost::get' : cannot convert parameter 2 from 'boost::detail::csr_edge_descriptor<Vertex,EdgeIndex>' to 'ptrdiff_t' c:\boost_1_49_0\boost_1_49_0\boost\graph\dijkstra_shortest_paths.hpp 162 I might be totally off here so please let me know :) Thanks! - Jeremy -- View this message in context: http://boost.2283326.n4.nabble.com/CSR-graph-and-Dijkstra-s-to-lower-graph-… Sent from the Boost - Users mailing list archive at Nabble.com.

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[Sandbox - endian] Why is endian still in sandbox?
by Nathaniel J Fries 07 Oct '12

07 Oct '12

A fairly novel (at least when put up against more intricate labours like asio, filesystem, and their like) project which appears to be finished and would be a very useful companion to existing libraries sits in the sandbox. Is there a reason for this?

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[BGL] vecS for vertex container and vertex index adjustments
by Sergey Mitsyn 03 Oct '12

03 Oct '12

Hi all, I know that while using vecS for vertices one has no vertex iterator stability upon removing vertices. But I have a question if there exists something like vertex _index_ stability. The documentation says that indices for vertices are automatically adjusted so that they are still in contiguous range, but it is not specified how it is done. Is it okay to assume that if a vertex with an index I is removed, then vertices with indices < I have their indices unchanged, while vertices with indices > I have their indices decreased by one? The actual problem is removing all vertices meeting some condition. Is the following code ok? // traverse all vertices and remove those for which predicate // condition_to_remove_vertex returns true. // graph is adjacency_list<.., vecS, ...> vertex_iterator vi = vertices(graph).first, vi_end = vertices(graph).second; while (vi != vi_end) { if (condition_to_remove_vertex(vi, graph)) { vertices_size_type end_index = vertex_index[*vi_end] , vi_index = vertex_index[*vi]; remove_vertex_f(*vi, graph); // vi and vi_end are invalid --end_index; vi = vertices(graph).first + vi_index; vi_end = vertices(graph).first + end_index; // now vi and vi_end are valid again } else ++vi; } This way seems to be more effective than to start iteration again every time a vertex is removed. ------------ Sergey Mitsyn.

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C++ (boost) library for serial port communication
by Alexander Dietz 03 Oct '12

03 Oct '12

Hi all, I wonder if there is a boost-library that enables easy and robust communication to a serial port, just as e.g. the python library pyserial does. Maybe there is a boost-library which can be used for those purpose instead of implementing my own C-style classes and functions? Thanks a lot, Alex

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