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[Graph] Adjacency list scalability with a Dijkstra algorithm
by Florian.PONROY＠fr.thalesgroup.com 27 Mar '09

27 Mar '09

Hi, Assuming that I want a graph made of 6 nodes, numbered 1, 2, 3, 4, 5 and 4242. I build the graph this way: typedef boost::adjacency_list<boost::listS, boost::vecS, boost::directedS, boost::no_property, boost::property<boost::edge_weight_t, int> > tGraphShortestpath; tGraphShortestpath graph; boost::add_edge(1, 2, 1234); // 1234 is the weight boost::add_edge(1, 3, 412); ... boost::add_edge(5, 2, 29); boost::add_edge(5, 4242, 84); boost::add_edge(4242, 2, 456); boost::add_edge(4242, 5, 680); Now, I want to apply the Dijkstra algorithm on this graph. I create a distance and a predecessor vector, as I have seen on the documentation online : typedef tGraphShortestpath::vertex_descriptor tVertex; std::vector<tVertex> predecessors(boost::num_vertices(graph)); std::vector<int> distances(boost::num_vertices(graph)); Here is the problem: I would have imagined that, in my case, boost::num_vertices(graph) would have returned 6, but it actually returns the higher vertex number + 1, that is... 4243 ! So each of my vector has a size of 4243 * sizeof(tVertex) bytes... Is there a way to handle that? I probably misuse the API, but it would be better if the container would be dimensioned to the actual number of vertices, since I am in a CPU and memory constraint environment... Thank you very much for your help! -- Florian PONROY Thales Land & Joint France Tel. : +33(0)1 41 304 363 Fax : +33(0)1 41 303 560 Email : florian.ponroy(a)fr.thalesgroup.com

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dijkstra and associative property map
by Sandeep Gupta 26 Mar '09

26 Mar '09

Hi, Attached below is the code to call Dijkstra over property_map data structures. The current definition of associative property map is incompatible for dijkstra. Somehow there is mismatch with respect to operator[]. Attach below is the code and the error. std::map<vertex_t, vertex_t> pred; boost::associative_property_map< std::map<vertex_t, vertex_t> > preds(pred); std::map<vertex_t, double> dist; boost::associative_property_map< std::map<vertex_t, double> > dists(dist); std::map<vertex_t, double> weight; boost::associative_property_map< std::map<vertex_t, double> > weights(weight); vertex_t v; //vertex_t v1 = preds[v]; dijkstra_shortest_paths(tg, v, predecessor_map(preds). weight_map(weights). distance_map(dists) ); Error: /home/sandeep/Computing/boost_1_38_0/boost/property_map.hpp:314: error: no match for ‘operator[]’ in ‘(const boost::associative_property_map<std::map<unsigned int, double, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, double> > > >&)((const boost::associative_property_map<std::map<unsigned int, double, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, double> > > >*)(& pa))[k]’ /home/sandeep/Computing/boost_1_38_0/boost/property_map.hpp:458: note: candidates are: typename UniquePairAssociativeContainer::value_type::second_type& boost::associative_property_map<UniquePairAssociativeContainer>::operator[](const typename UniquePairAssociativeContainer::key_type&) const [with UniquePairAssociativeContainer = std::map<unsigned int, double, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, double> > >] Thanks sandeep

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How do i only get Regex??
by Green, Jason M NSWCDL, W33 26 Mar '09

26 Mar '09

I'm using VC++ 8 and I am trying to use the boost regex in order to use regular expressions. I can get it to work, but it requires 60mb of files! What is the simplest, smallest subset of files that I need to get this to work. If there is a way to only have to import a dll or lib, that would be ideal. I would like it to be separate and standalone from the massive file collection that comes with boost as a whole. Please help! Thanks, Jason

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[Date_Time] compile errors with gcc 4.3
by Pearl Rothman 26 Mar '09

26 Mar '09

I am using Fedora 9, gcc 4.3.0, and boost 1.38.0. When I include <boost/date_time/posix_time/posix_time_types.hpp> I get the following errors /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:67: error: ‘::clock_t’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:68: error: ‘::time_t’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:71: error: ‘::clock’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:72: error: ‘::difftime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:73: error: ‘::mktime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:74: error: ‘::time’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:75: error: ‘::asctime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:76: error: ‘::ctime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:77: error: ‘::gmtime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:78: error: ‘::localtime’ has not been declared /usr/lib/gcc/x86_64-redhat-linux/4.3.0/../../../../include/c++/4.3.0/ctime:79: error: ‘::strftime’ has not been declared How can I resolve them? Thanks

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boost::asio memory buffers and persistent connections.
by Alejandro Martinez 26 Mar '09

26 Mar '09

I have a server running with asio. At any time i have 5000+ persistent connections from clients, but not all of them are sending/receiving data at all times. In fact, they only do requests once in a while. The problem is (with my current approach) that i need to have 5000+ memory buffers ready to receive that requests of very varying length. How could i make it so i can set the buffer to use at the exact moment in which data for a new request in an already open connection begins to arrive? And maybe have those buffers in some memory pool. I've been studying http://www.boost.org/doc/libs/1_38_0/doc/html/boost_asio/example/allocation… without understanding it completely, but it doesn't look like what im looking for. Any ideas? Thanks a lot in advance. Alejandro

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multithreaded timer?
by Francisco Ares 26 Mar '09

26 Mar '09

Hi I'm implementing an application, serial RS232 communications centered, using boost in Windows. Many of the user actions are translated to ASCII commands to be sent to some serial devices connected to the serial ports, but as they are quite slow, I had to implement a command queue, so that as soon as a command gets its answer, it is cleared and the next one is sent, up to the end of the queue (of course). Using boost serial communication features, I realized that I needed an extra time-out, because the devices are real slow. So that this low speed doesn't lock up anything, the command queue runs in a separate thread and I would like another thread to run a timer, that could be activated when the command is send by the queue thread, and deactivated by the same thread if it detects an answer coming from the device in response to its command. If the timer is due, it should send a signal or call a callback function in the queue thread so it knows that the last command timed-out and it should re-send it again. All the queue things are OK (so it seems for now), I just need the timer. The ASIO timer is quite strange to me, I didn't manage to make it work. I have already seen the "timers" tutorials at boost web pages, and none have worked for me as expected. Any ideas / suggestions / snippets? Thanks a lot Francisco -- "If you have an apple and I have an apple and we exchange apples then you and I will still each have one apple. But if you have an idea and I have one idea and we exchange these ideas, then each of us will have two ideas." - George Bernard Shaw

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[MPL] MPL use cases overview
by Olivier Tournaire 26 Mar '09

26 Mar '09

Hi all, I am currently reading "C++ template metaprogramming" and I am very interested in the MPL provided by boost. However, I am curious on how users integrate this library in their developments. Please feel free to post not only code snippets, but also description of your usages of the MPL ! Thanks, Olivier

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[gil] Unexplainable compiler error
by Robert Dailey 26 Mar '09

26 Mar '09

Below is the compiler error that I'm getting in Visual Studio 2008: C:\IT\work\redsword\third_party\boost\1_38_0\boost/gil/image.hpp(119) : error C2039: '_view' : is not a member of 'boost::gil::image_view<Loc>' with [ Loc=boost::gil::rgba8c_loc_t ] ..\..\..\..\components\libs\renderer\source\Image.cpp(44) : see reference to function template instantiation 'boost::gil::image<Pixel,IsPlanar,Alloc> &boost::gil::image<Pixel,IsPlanar,Alloc>::operator =<boost::gil::image_view<Loc>>(const Img &)' being compiled with [ Pixel=boost::gil::rgba8_pixel_t, IsPlanar=false, Alloc=std::allocator<unsigned char>, Loc=boost::gil::rgba8c_loc_t, Img=boost::gil::image_view<boost::gil::rgba8c_loc_t> ] And the code that it is compiling: #include <boost/gil/image_view.hpp> #include <boost/gil/image.hpp> #include <boost/gil/typedefs.hpp> Image::Image( unsigned char const* buffer, unsigned int width, unsigned int height, unsigned int bitsPerPixel, int pitch ) { // Provide a pitch the exact width of the image if no // explicit pitch was provided. if( !pitch ) { pitch = width * bitsPerPixel; } using namespace boost::gil; m_imageData = interleaved_view( width, height, reinterpret_cast<rgba8_pixel_t const*>( buffer ), pitch ); } I'm still new to boost::gil and it's very hard to learn. Can anyone guide me in the right direction as to how to resolve this compiler error?

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Re: [Boost-users] boost::array and lower_bound
by Hicham Mouline 26 Mar '09

26 Mar '09

I just didn't the see the std::lower_bound version with the comparator. That does what I want, Regards. > -----Original Message----- > From: Hicham Mouline [mailto:hicham@mouline.org] > Sent: 26 March 2009 9:30 > To: 'boost-users(a)lists.boost.org' > Subject: boost::array and lower_bound > > Hello, > I maintain a boost::array< pair< time, value > > B, > sorted by time, where I defined operator< for pair<time, value> > > I wish to get a given entry from the array for a given time y. > > If y matches any entry, value is returned, if y is between 2 entries, an > interpolated value is returned. > > std::lower_bound( &B[0], &B[supSize], ... ) //this doesn't work > > I suppose for this I need to define some other related iterator to pass to > lower_bound, > not boost::array< pair< time, value > >::const_iterator. > > I suppose this is what "Iterator adaptors" are about ? > I have seen the term "views" as well, is this related? > > Regards,

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boost::array and lower_bound
by Hicham Mouline 26 Mar '09

26 Mar '09

Hello, I maintain a boost::array< pair< time, value > > B, sorted by time, where I defined operator< for pair<time, value> I wish to get a given entry from the array for a given time y. If y matches any entry, value is returned, if y is between 2 entries, an interpolated value is returned. std::lower_bound( &B[0], &B[supSize], ... ) //this doesn't work I suppose for this I need to define some other related iterator to pass to lower_bound, not boost::array< pair< time, value > >::const_iterator. I suppose this is what "Iterator adaptors" are about ? I have seen the term "views" as well, is this related? Regards,

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