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Re: [Boost-users] Q: Graphs. Sorting edges. Possible? How to?
by Jeff Holle 21 Nov '05

21 Nov '05

I've found this partial solution for what I'm searching for. This code sorts by target, name. I want to sort by source, target. I find that in boost::graph adjacency_list edge descriptors there is a "get_target" method, but no "get_source" method. Can someone tell me how to either find the equivalent or give the comparison function object a non-default constructor so I can pass it a graph reference? Actually in the latter, I need assistance in feeding the graph reference to the graph object at construction time, not writing a constructor. Jeremy Siek wrote: > On Wed, 19 Jun 2002, stas_fomin wrote: > stas_f> > By using a custom container (use a std::set with your custom > stas_f> comparison > stas_f> > function) for the EdgeList type, you can get the out-edges of each > stas_f> vertex > stas_f> > sorted, but there currently is not a way to get the entire edge list > stas_f> > sorted. > stas_f> Ok... But BGL docs is less understandable (in comparison with > stas_f> LEDAbook) for me (I know I am stupid). > > Have you tried reading the BGL book? > > stas_f> So, please, show me small example of declaration > stas_f> of some graph with out_edges sorted according to some function... > > Here you go. Also, this example is checked into the libs/graph/example/ > directory. > > #include <boost/config.hpp> > #include <iostream> > #include <functional> > #include <string> > > #include <boost/graph/adjacency_list.hpp> > #include <boost/graph/properties.hpp> > > /* > Sample output: > > 0 --chandler--> 1 --joe--> 1 > 1 --chandler--> 0 --joe--> 0 --curly--> 2 --dick--> 3 --dick--> > 3 > 2 --curly--> 1 --tom--> 4 > 3 --dick--> 1 --dick--> 1 --harry--> 4 > 4 --tom--> 2 --harry--> 3 > > name(0,1) = chandler > > name(0,1) = chandler > name(0,1) = joe > > */ > > template <class StoredEdge> > struct order_by_name > : public std::binary_function<StoredEdge,StoredEdge,bool> > { > bool operator()(const StoredEdge& e1, const StoredEdge& e2) const { > // Order by target vertex, then by name. > // std::pair's operator< does a nice job of implementing > // lexicographical compare on tuples. > return std::make_pair(e1.get_target(), boost::get(boost::edge_name, > e1)) > < std::make_pair(e2.get_target(), boost::get(boost::edge_name, e2)); > } > }; > struct ordered_set_by_nameS { }; > > #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION > namespace boost { > template <class ValueType> > struct container_gen<ordered_set_by_nameS, ValueType> { > typedef std::multiset<ValueType, order_by_name<ValueType> > type; > }; > template <> > struct parallel_edge_traits<ordered_set_by_nameS> { > typedef allow_parallel_edge_tag type; > }; > } > #endif > int > main() > { > #ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION > std::cout << "This program requires partial specialization" << > std::endl; > #else > using namespace boost; > typedef property<edge_name_t, std::string> EdgeProperty; > typedef adjacency_list<ordered_set_by_nameS, vecS, undirectedS, > no_property, EdgeProperty> graph_type; > graph_type g; > > add_edge(0, 1, EdgeProperty("joe"), g); > add_edge(1, 2, EdgeProperty("curly"), g); > add_edge(1, 3, EdgeProperty("dick"), g); > add_edge(1, 3, EdgeProperty("dick"), g); > add_edge(2, 4, EdgeProperty("tom"), g); > add_edge(3, 4, EdgeProperty("harry"), g); > add_edge(0, 1, EdgeProperty("chandler"), g); > > property_map<graph_type, vertex_index_t>::type id = get(vertex_index, > g); > property_map<graph_type, edge_name_t>::type name = get(edge_name, g); > > graph_traits<graph_type>::vertex_iterator i, end; > graph_traits<graph_type>::out_edge_iterator ei, edge_end; > for (boost::tie(i, end) = vertices(g); i != end; ++i) { > std::cout << id[*i] << " "; > for (boost::tie(ei, edge_end) = out_edges(*i, g); ei != edge_end; > ++ei) > std::cout << " --" << name[*ei] << "--> " << id[target(*ei, g)] << " > "; > std::cout << std::endl; > } > std::cout << std::endl; > > bool found; > typedef graph_traits<graph_type> Traits; > Traits::edge_descriptor e; > Traits::out_edge_iterator e_first, e_last; > > tie(e, found) = edge(0, 1, g); > if (found) > std::cout << "name(0,1) = " << name[e] << std::endl; > else > std::cout << "not found" << std::endl; > std::cout << std::endl; > > tie(e_first, e_last) = edge_range(0, 1, g); > while (e_first != e_last) > std::cout << "name(0,1) = " << name[*e_first++] << std::endl; > #endif > return 0; > } > > > > ---------------------------------------------------------------------- > Jeremy Siek http://php.indiana.edu/~jsiek/ > Ph.D. Student, Indiana Univ. B'ton email: jsiek(a)osl.iu.edu > C++ Booster (http://www.boost.org) office phone: (812) 855-3608 > ---------------------------------------------------------------------- > > >

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Boost::thread scheduling under HPUX
by Pete 21 Nov '05

21 Nov '05

Under heavy load, my HP-UX 11i application can run multiple, CPU intensive boost::thread's. Unfortunately, this has the side effect that other processes suffer in terms of performance. I initially thought that decreasing the nice value of my app would do the trick and ensure that other processes with a higher value would get priority by the kernel scheduler. However, this does not appear to be true (my app's nice value is 30 when most other processes run at 20). The requirement of my app is to run only whenever the system is idle. Is there a way this can be done using boost::thread or does anybody know how I could configure my process under HP-UX so that it behaves as intended?

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program_options: St9exception Exception?
by Merrill Cornish 21 Nov '05

21 Nov '05

I posted a question earlier about why I couldn't get Boost 1.33.0 program_options to "see" my positional parameter and why it bombed on unexpected options. Volodya pointed out that an illegal option throws an exception and asked if I had a catch. I felt like a fool for forgetting exceptions and through that was the problem. Then I looked at the code again. The method that uses program_options to read the command line had no try/catch, but the main program that called that method DID have the call wrapped in a try that has catches both for std::exception and (...). And yet, it wasn't trapping anything. Between ZoneAlert and Windows, I *think* I know the problem: something is attempting to access NULL, so I'm getting an OS memory error that C++ exceptions can't catch. I moved try's and catch's around in the code until I found the offending statement: po::variables_map vm; ...a declaration of all things. Here's an excerpt of the code po::options_description desc("Options"); desc.add_options() ("help,h", " Display this help message.") ("version", " Display the version.") // ... other options ;//add-options() // specify the single, required graph file positional parameter po::positional_options_description pd; pd.add("graph_file", 1); po::variables_map vm; //<============== try { po::store(po::command_line_parser(argc, argv). options(desc). positional(pd). run(), vm); po::notify(vm); // ... other code that references vm }//try catch(std::exception e) { cerr << "Exception:" << endl; cerr << e.what() << endl; exit(EXIT_FAILURE); }//catch catch(...) { cerr << "An unknown exception occurs while parsing : "command line arguments." << endl; exit(EXIT_FAILURE); }//catch Using the 'try' in the position shown above, if I input an unexpected command line options, an exceptioin is thrown whose what() method returns "St9exception". That's it. Just "St9exception". I can't find that string in the Boost source anywhere. However, if I move the "try" up one statement so it's above "po::variables_map vm;", then there's no exceptoin, but the access to location 0. That's one picky declaration. Merrill

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multi_array - changing number of elements
by fritz.birnbacher＠t-online.de 21 Nov '05

21 Nov '05

Hello, how can I change the number of elements in an array ? I want to do following: typedef boost::multi_array<double, 2> array_type; array_type::extent_gen extents; array_type A1(extents[2][3]); array_type A2; A2 = A1 best regards Fritz Birnbacher

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[BGL, Graph] choose the correct container to handle graph with a property
by Johan Oudinet 21 Nov '05

21 Nov '05

Hello, I have a graph representing the Network topology and I want to replace it by a BGL graph. My problem is that I need to find a vertex by its IP address (an internal property), but I think we can only find a vertex with its vertex_descriptor. A solution is to maintain a map from IP address to vertex_descriptor. But removing a vertex with vecS for VertexList invalidates all vertex descriptors. Unfortunately, I need some efficiently to find a vertex, so listS seems not appropriated. Finally, I try to use setS for VertexList (and it works IMHO), but in the documentation: "The container must model Sequence or RandomAccessContainer." Hence, my questions are: - Can I use setS for VertexList ? And if I can't, why ? - Is there a better solution to find vertex by an internal property that handle an exterior map ? Cheers, -- Johan

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Re: [Boost-users] Unknown program_options bomb
by Merrill Cornish 21 Nov '05

21 Nov '05

Volodya, Sorry about the formatting. It annoys me too. However, I'm using Earthlink's online Web Mail, so I'm stuck with some of their choices. There new mail (available RSN) may have a formatting option. RE: exception DOH! I should have thought of that. For everything else, I'm always very careful to check for exceptions. In this case, I tacitly assume it worked like getopts and just left unknown options on the command line. (Old habits die hard.) I haven't got time to try now, but I will put in the exception handlers and see what it's complaining about with my positional parameter. I realize that "bomb" wasn't very precise, but it was hard to describe what happened. First, Zone Alert would become excited and claim that my program was attempting to do something "dangerous". (Yes, that should have clued me in to an exception being thrown, but I was dense.) If I told Zone Alert to let it happen, then Windows popped up a dialog offering to send a report to Microsoft about my incompetence. :-) Thanks for your help. Merrill

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boost::thread - mistake in documentation
by Oliver.Kowalke＠infineon.com 21 Nov '05

21 Nov '05

Hello, the documentation (http://www.boost.org/doc/html/condition.html) of class condition contains a mistake: instead of template<typename ScopedLock, typename Pred> bool timed_wait <http://www.boost.org/doc/html/condition.html> (ScopedLock&, Pred); it should be template<typename ScopedLock, typename Pred> bool timed_wait <http://www.boost.org/doc/html/condition.html> (ScopedLock&, const boost::xtime <http://www.boost.org/doc/html/xtime.html> & , Pred); so long, Oliver

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contribution - sync. queue between producer/consumer threads
by Oliver.Kowalke＠infineon.com 21 Nov '05

21 Nov '05

Hello, I would contribute this code. The queue synchronizes the access between producer threads (putting items into the queue) and consumer threads (removing items from queue). I would be glad if you add this code to boost::thread library. With regards, Oliver <<queue.hpp>> <<test.cpp>>

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Re: [Boost-users] Unknown program_options bomb
by Merrill Cornish 21 Nov '05

21 Nov '05

Will, I've changed my original po::store(parse_command_line(argc, argv, desc), vm); to po::store(po::command_line_parser(argc, argv). options(desc). positional(pd). run(), vm); where desc is is an options_description and pd is a positional_options_description. This looks like an exact match for po::variables_map vm; po::store(po::command_line_parser(ac, av). options(desc).positional(p).run(), vm); po::notify(vm); which is the example from http://www.boost.org/doc/html/program_options/tutorial.html. However, the code still bombs if I give it a positional parameter or an option it isn't expecting. Merrill

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Re: [Boost-users] Unknown program_options bomb
by Merrill Cornish 21 Nov '05

21 Nov '05

Liam, I think you're right, but I haven't been able to figure out the exact incantation. :-) Merrill

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