June 2003 - Boost-users - lists.boost.org

boost::shared_ptr and stl algorithms
by Bill Eidson 15 Apr '05

15 Apr '05

std::vector< boost::shared_ptr<T> > TVec; I want to write a function object to run std::for_each. to do somework against members of T and accumulate results in functor. My attempts have failed in VC7 with memory errors in my operator() method. struct fo { bool operator()( boost::shared_ptr<T>& t ) { return true; } }; Thanks in advance bille

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BGL and reversing / moving edges
by joshrose 17 Dec '03

17 Dec '03

G'day, I was hoping someone might be able to tell me if they've run into any situations using BGL where they needed to move (or reverse (i.e. flip the source and target)) an edge within a graph implemented as an adjacency_list. I'm working on an implementation of an algorithm for max. weight bipartite matching ("the assignment problem"), and one of the assumptions in the algorithm is that non-matched edges are directed from one subgraph, A, to the other subgraph, B, and matched edges are directed the other way. Over the course of growing the matching, a simple way to add and remove edges from the candidate set is just to reverse the edge, thus the need for some way to reverse the edge within BGL. I don't think I can just remove and then re-add the edge in the other direction, primarily because doing so will (I believe) invalidate any edge_descriptors referring to that edge. In particular, there are property maps keeping track of the weight of edges, the predecessors of certain nodes, etc. that use edge descriptors as keys. I've spent a fair bit of time reading the documentation and looking through the implementation of adjacency_lists (incl. edge_list_impl), and I'm not really sure of a way to either move an edge directly within a graph, or even to create a new edge from another s.t. they have the same edge_descriptor (in general a bad thing, probably). Anyone have any thoughts on this? Thanks, -Josh

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Graph Library: Ordered Vertex List?
by dmatt001 01 Aug '03

01 Aug '03

Hi Guys, I would like to use an ordered vertex list (ie based on property type) in an implementation that I am working on such that duplication can be avoided. I have read and understand how to implement an ordered edge list thanks to the previous posts but am finding it hard to get started! Perhaps I have missed the key example? It appears that from the way config::VertList is constructed that it may be a similar process in nature? adj_list_impl::add_vertex appears to discard the boolean return value from the associative insertion. Would such a construction allow me to avoid the duplication I seek to avoid? I am guessing so, but some advice would give me a confidence "boost". ( <-- It's a lame pun: I really do need help ;-) ) My first steps are below rehashing the excellent ordered edges example with a simple search/replace and maching my target container base. I'll keep plugging along with it anyway and it may just compile one day. Suggestions/Ideas/Refs/Ptrs are appreciated. Matt --- first guess follows --- template <class VertDesc> struct order_by_name : public std::binary_function<VertDesc,VertDesc,bool> { bool operator()(const VertDesc& v1, const VertDesc& v2) const { // Order by vertex name. return boost::get(boost::vertex_name, v1) < boost::get(boost::vertex_name, v2); } }; #if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION struct ordered_set_by_nameS { }; namespace boost { template <class ValueType> struct container_gen<ordered_set_by_nameS, ValueType> { typedef std::set<ValueType, order_by_name<ValueType> > type; }; } #else struct ordered_set_by_nameS { template <class T> struct bind_ { typedef std::multiset<T, order_by_name<T> > type; }; }; namespace boost { template <> struct container_selector<ordered_set_by_nameS> { typedef ordered_set_by_nameS type; }; } #endif

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libbgl-viz.a instead of libbglviz.a
by dhofstee 16 Jul '03

16 Jul '03

Hi, I'm quite new at using boost (downloaded 1.30.0 a couple of days ago). I noticed that when I wanted to make libbglviz.a, as described in http://www.boost.org/libs/graph/doc/read-graphviz.html, there was already a makefile. "make libbglviz.a" does not work, but "make libbgl-viz.a" will. A second documentation error is in http://www.boost.org/libs/property_map/property_map.html, where the example is not equal to the actual cpp file. generic_foo_algorithm is on this page, but the file just mentions foo. I think it is a glitch in the doc, but if different... Comments?, David NL

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Having problems with boost::signal and boost::function
by subsample 11 Jul '03

11 Jul '03

I'm having a problem (which was really hard to decipher) when connecting a function object to a signal. Thing is I default construct (no argument) a function object and connect it to the signal (using boost::ref), then at a later point in time I actually assign something to the function object (using boost::bind). But firing the signal after this causes a bad_function_call to be thrown. On the other hand; if I construct the function object with some dummy object before connecting it to the signal, and later do the assignment, the signal does its thing. If someone could enlighten me as to whats going on here, I'd be grateful .. : )

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Signals library safety
by Eugene Talagrand 11 Jul '03

11 Jul '03

Hello to all, I'm looking into using the Boost.Signals. The library claims not to be thread safe. What does this mean exactly? When using Boost.Threads, can I make concurrent calls to connect as long as I wrap each call in a Mutex? If this is possible, do tackable objects also still work (if two trackable objects get destroyed in two different threads there might be a problem from what I understand) On an different note, I am trying to use Boost.Signals for network event handling. I'd like to set it up so that it uses something similar to he JavaScript event model, where every slot returns a boolean value. If that value is false, the remaining slots are not called. Would anyone have any recommendations on how to do this? Should I wrap each slot in a function that takes the return value and sets a global flag, then every subsequent slot checks the flag? It looks like combiners would not be appropriate, as it appears they are used after each slot is called (unless the InputIterator' opeator* actually calls the slot??) Thanks for any help -Eugene

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Boost.Thread and fork
by Pavol Droba 02 Jul '03

02 Jul '03

Hi, I have problem with boost.threads on linux ( under gcc ). I have a multithreaded aplication using Boost.Thread. It works just fine. However, I want to make a daemon out of it. So I tried to fork() at the start of the program and run all the relevant code ( including all threading ) in the child process. But when I do so, first call to create_thread hangs the process. I'm quite new to linux threading, so it is possible, that the problem is not related to Boost.Threads. Any hints? Thanks in advance. Pavol

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newbie bjam question
by Karsten Weinert 30 Jun '03

30 Jun '03

Hi, there are two questions about bjam I tried to answer, but failed: * which files are read by bjam in which order * where can I declare the standard include path I am using mingw on win98. Would be nice if someone could help me here, Karsten Weinert

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BGL problem with filtered_graph and adjacency_matrix
by Matthias Rupp 30 Jun '03

30 Jun '03

Hi, i'm new to boost and encountered the following problem with the boost graph library and this code: #include "boost/graph/adjacency_list.hpp" #include "boost/graph/adjacency_matrix.hpp" #include "boost/graph/filtered_graph.hpp" int main (void) { using namespace boost; typedef adjacency_matrix<undirectedS> Graph; //typedef adjacency_list<vecS, vecS, undirectedS> Graph; typedef filtered_graph<Graph, keep_all> FilteredGraph; Graph g (5); FilteredGraph fg (g, keep_all ()); } This results in a lot of error messages from the compiler (see end of email), all located in the bgl files. If i use adjacency_list (as in the commented line above) instead of adjacency_matrix, everything's fine. I use gcc 3.3 under linux and version 1.30 of the boost library. Is this a bug? Is there an easy way to make filtered_graph work with adjacency_matrix? (I'd like to use adjacency_matrix because my graphs are almost complete graphs). Best regards, Matthias Rupp The first error messages from the compiler (the rest are also complaints about forming references to void): ../boost_1_30_0/boost/iterator_adaptors.hpp: In instantiation of `boost::iterator_adaptor<void, boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>*, boost::multi_pass_input_iterator_tag, ptrdiff_t>': ../boost_1_30_0/boost/graph/filtered_graph.hpp:216: instantiated from `boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all>' complaint.cpp:23: instantiated from here ../boost_1_30_0/boost/iterator_adaptors.hpp:852: error: forming reference to void ../boost_1_30_0/boost/iterator_adaptors.hpp:927: error: forming reference to void ../boost_1_30_0/boost/iterator_adaptors.hpp: In instantiation of `boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>': ../boost_1_30_0/boost/type_traits/is_convertible.hpp:128: instantiated from `boost::detail::is_convertible_basic_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>&, boost::detail::int_convertible>' ../boost_1_30_0/boost/type_traits/is_convertible.hpp:191: instantiated from `boost::detail::is_convertible_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>&, boost::detail::int_convertible>' ../boost_1_30_0/boost/type_traits/is_enum.hpp:91: instantiated from `boost::is_convertible<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>&, boost::detail::int_convertible>' ../boost_1_30_0/boost/type_traits/is_enum.hpp:91: instantiated from `boost::detail::is_enum_helper<false>::type<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>&>' ../boost_1_30_0/boost/type_traits/is_enum.hpp:91: instantiated from `boost::detail::is_enum_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_scalar.hpp:36: instantiated from `boost::is_enum<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_scalar.hpp:36: instantiated from `boost::detail::is_scalar_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_class.hpp:76: instantiated from `boost::is_scalar<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_class.hpp:76: instantiated from `boost::detail::is_class_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_empty.hpp:75: instantiated from `boost::is_class<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/type_traits/is_empty.hpp:75: instantiated from `boost::detail::is_empty_impl<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/iterator_adaptors.hpp:934: instantiated from `boost::is_empty<boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/iterator_adaptors.hpp:934: instantiated from `boost::compressed_pair<void, boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void> >' ../boost_1_30_0/boost/iterator_adaptors.hpp:934: instantiated from `boost::iterator_adaptor<void, boost::filter_iterator_policies<boost::detail::in_edge_predicate<boost::keep_all, boost::keep_all, boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all> >, void>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>, boost::detail::matrix_edge_desc_impl<boost::undirected_tag, size_t>*, boost::multi_pass_input_iterator_tag, ptrdiff_t>' ../boost_1_30_0/boost/graph/filtered_graph.hpp:216: instantiated from `boost::filtered_graph<main()::Graph, boost::keep_all, boost::keep_all>' complaint.cpp:23: instantiated from here ../boost_1_30_0/boost/iterator_adaptors.hpp:1313: error: forming reference to void ../boost_1_30_0/boost/iterator_adaptors.hpp:1315: error: forming reference to void ../boost_1_30_0/boost/iterator_adaptors.hpp:1344: error: forming reference to void [...]

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New file uploaded to Boost-Users
by Boost-Users＠yahoogroups.com 30 Jun '03

30 Jun '03

Hello, This email message is a notification to let you know that a file has been uploaded to the Files area of the Boost-Users group. File : /uBLA Performance.pdf Uploaded by : sumohurd <matt(a)finray.net> Description : Updated to correctly use n^2*(2n-1) for notional FLOP count You can access this file at the URL http://groups.yahoo.com/group/Boost-Users/files/uBLA%20Performance.pdf To learn more about file sharing for your group, please visit http://help.yahoo.com/help/us/groups/files Regards, sumohurd <matt(a)finray.net>

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