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[multi_index] problem with hashed index
by Boris 21 Mar '07

21 Mar '07

I've been using Boost Multiindex quite a lot but don't understand why the code below inserts two items. The container has a unique hash index and the two items return the same hash value. Is this is a bug in the library or in my code? Boris -- struct foo { int i, j; foo(int i, int j) : i(i), j(j) { } }; std::size_t hash_value(const shared_ptr<foo> &f) { std::size_t seed = 0; boost::hash_combine(seed, f->i); boost::hash_combine(seed, f->j); return seed; } typedef multi_index_container< shared_ptr<foo>, indexed_by<hashed_unique<identity<shared_ptr<foo> > > > > mi_t; shared_ptr<foo> f1(new foo(0, 0)); shared_ptr<foo> f2(new foo(0, 0)); mi_t mi; cout << mi.insert(f1).second << endl; // Returns 1. cout << mi.insert(f2).second << endl; // Returns again 1?! cout << mi.size() << endl; // Returns 2?!

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[fusion] Weird compiler error
by Christian Henning 21 Mar '07

21 Mar '07

Hi there, I know the subject looks suspicious. Usually all compiler errors are weird when you do metaprogramming. Anyway, this example is a bit different. I'm just trying to compile a small example taking from the documentation. #include <boost/fusion/sequence.hpp> using namespace std; using namespace boost; using namespace fusion; int _tmain(int argc, _TCHAR* argv[]) { typedef map<pair<int, char>, pair<char, char>, pair<double, char> > mymap; BOOST_MPL_ASSERT((boost::is_same<result_of::at_key<mymap, int>::type, char&>)); return 0; } The error is: c:\cybermdx\Test Programs\Boost\MPL\tagged types\tagged types.cpp(15) : error C2143: syntax error : missing '}' before '(' c:\cybermdx\Test Programs\Boost\MPL\tagged types\tagged types.cpp(15) : fatal error C1903: unable to recover from previous error(s); stopping compilation I have no clue where the compiler is missing a closing bracket. I'm using MSVC 7.1 Christian

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polymorphic_downcast and references
by Michael Marcin 21 Mar '07

21 Mar '07

Unless I'm missing something it looks like polymorphic_downcast doesn't provide an overload for reference types... is there a reason? This makes it a little inconvenient for use. Thanks, Michael Marcin

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[Test] BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES => exceptions?
by Sohail Somani 21 Mar '07

21 Mar '07

Hi, Does Boost.Test consider an exception as a failure? How can I make it expect an exception? Or is there another way to do this? Thanks, Sohail

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iostreams crash
by Aljaz 21 Mar '07

21 Mar '07

Hello I've been working with boost iostreams filters. Since when I changed fin.push(file_source("outest.fil", ios::in | ios::binary)); to: file_source fss("outest.fil", ios::in | ios::binary); fin.push(boost::ref(fss)); file crashes when the task is done. Why is that happening? What am I doing wrong? I think it has something to do with memory allocation.. Another thing im unsure about: Should I open file each time I want to read from it, or can I open it at program start, and leave it open (program will be running for a long period) ? I hope someone responds this time Thanks for help Best regards #include <boost/iostreams/device/file.hpp> #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/filter/line.hpp> #include <boost/ref.hpp> #include <exception> #include <fstream> #include <ostream> #include <iostream> #include <string> #include <vector> using namespace std; using namespace boost::iostreams; namespace io = boost::iostreams; class long_line_counter : public boost::iostreams::line_filter { public: explicit long_line_counter(int max_length = 80) : max_(max_length), count_(0) { } int count() const { return count_; } vector<string> mail_list; private: std::string do_filter(const std::string& line) { if (line.size() < max_) mail_list.push_back(line); ++count_; return line; } int max_; int count_; }; int main() { try { filtering_istream fin; long_line_counter llc(80); file_source fss("outest.fil", ios::in | ios::binary); fin.push(boost::ref(llc)); fin.push(boost::ref(fss)); char buf[4012]; while ( fin.read(buf, 4012) ) { } std::cout << llc.count() << "\n"; std::cout << llc.mail_list.size() << "\n"; } catch (exception &e) { cout << "exception: " << e.what() << std::endl; } return 0; }

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[BGL] Problems implementing a special DFS algorithm
by Ignaz Rutter 21 Mar '07

21 Mar '07

Hi, I'm currently trying to implement an algorithm that basically is a DFS. The description looks roughly like this: Start a DFS, when going down an edge (e.g. put it into the tree): do something when backtracking an edge (e.g. move upwards in the search tree): do something else I tried to implement this using the DFS Visitor concept. However it seems like the appropriate events are not defined in this concept. Am I missing something here? Is it possible to reuse depth_first_search here? Or should I just I go ahead and implement my own DFS? Thanks, Ignaz

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tutorial or book on boost
by Vaclav 21 Mar '07

21 Mar '07

Hello, Can you please recommend a good tutorial or book on boost library for beginners? Thanks Vaclav

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Uninitialised value issue with serialization of std::vector<double>
by Jonathan Cooper 21 Mar '07

21 Mar '07

Hi. In using valgrind to run memory tests of our software, we've been getting 'Conditional jump or move depends on uninitialised value(s)' errors which appear to be caused by Boost's serialization library. Specifically, they occur on loading a std::vector<double> from a text archive. A simple test program which demonstrates this behaviour is shown below, together with a snippet from valgrind's output. Incidentally, deserializing std::vector<bool> does not have this problem, and specializing boost::serialization::{save,load} for vector as for bool makes the problem go away. Any ideas? Jonathan. Boost version: 1.33.1 Valgrind version: 3.2.1 System: Fedora Core 6 g++ (GCC) 4.1.1 20061011 (Red Hat 4.1.1-30) Test program, which compiles and runs as expected: #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/serialization/vector.hpp> #include <fstream> #include <cmath> #include <cassert> int main(void) { std::string archive_filename("simple_vars.arch"); // Create an ouput archive { std::ofstream ofs(archive_filename.c_str()); boost::archive::text_oarchive output_arch(ofs); std::vector<double> doubles(3); doubles[0] = 1.1; doubles[1] = 1.2; doubles[2] = 1.3; // cast to const and write output_arch << static_cast<const std::vector<double>&>(doubles); } { // Create an input archive std::ifstream ifs(archive_filename.c_str(), std::ios::binary); boost::archive::text_iarchive input_arch(ifs); std::vector<double> doubles; // read the archive input_arch >> doubles; // test values assert(doubles.size() == 3u); assert(fabs(doubles[0] - 1.1) < 1e-12); assert(fabs(doubles[1] - 1.2) < 1e-12); assert(fabs(doubles[2] - 1.3) < 1e-12); } return 0; } Excerpt from valgrind stack trace: ==10018== Conditional jump or move depends on uninitialised value(s) ==10018== at 0x403C0ED: boost::archive::detail::basic_iarchive::reset_object_address(void const*, void const*) (in /usr/lib/libboost_serialization.so.1.33.1) ==10018== by 0x804E23E: boost::serialization::stl::archive_input_seq<boost::archive::text_iarchive, std::vector<double, std::allocator<double> > >::operator()(boost::archive::text_iarchive&, std::vector<double, std::allocator<double> >&) (collections_load_imp.hpp:54) ... ==10018== by 0x80506A7: boost::archive::text_iarchive& boost::archive::detail::interface_iarchive<boost::archive::text_iarchive>::operator>><std::vector<double, std::allocator<double> > >(std::vector<double, std::allocator<double> >&) (interface_iarchive.hpp:76) ==10018== by 0x804B7F2: main (serialize_bug.cpp:40) -- Jonathan Cooper MSN: msn(a)jonc.me.uk www: jonc.me.uk/ I never learned anything while I was talking - Larry King

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[timer] How to change format of progres_display
by Seweryn Habdank-Wojewódzki 21 Mar '07

21 Mar '07

Hi Is there any easy way to change format in progress_display? Change: - Length of axis; - Number of thicks; - Labels on axis e.g. "A", "B", "C" or 1.0, 3.14, 5.12. Motivation for changing labels. If I have strings in vector and for me better is not to use 20%, but to use letters. I can take the first letter(s) of word on position "20%" and display it as label. Is it possible? Regards. -- |\/\/| Seweryn Habdank-Wojewódzki \/\/

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BGL graph library biconnected components
by Greg Reynolds 21 Mar '07

21 Mar '07

Hi, I have been using "biconnected_components.hpp" for quite a while now. However, I have come across some graphs for which it finds far too many components... Here is my usage: //////////////////////////// Graph g; // initialise g and give edges an index std::vector< int > vec_bcc_nums( num_edges(g) ); iterator_property_map< std::vector< int >::iterator, property_map<Graph, edge_index_t>::type > mapEdgeComponent( vec_bcc_nums.begin() ); int num = biconnected_components(g, mapEdgeComponent); /////////////////////////// I'm afraid I can't post an example of the graphs (they are really big and I signed an NDA). What I would like to know is: a) Is the code above sensible, is there something subtly wrong with it? b) Has anyone else used the biconnected components code in anger on largish (> 300 vertices) graphs? Thanks, Greg

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