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

Accessing exterior graph properties by name
by David Doria 26 Jan '12

26 Jan '12

Is there a way to "associate" an external property map to a name so that it can be retrieved from the graph? With a standard interior property, you can do: // Declare that you will be able to identify a property map by "vertex_data" namespace boost { enum vertex_data_t { vertex_data }; BOOST_INSTALL_PROPERTY(vertex, data); }; // Get the vertex_data property map from the graph typedef boost::property_map<Graph, boost::vertex_data_t>::type PropertyMapType; PropertyMapType propertyMap = get(boost::vertex_data, g); However, with the exterior properties, I can associate the property map with the nodes of the graph: typedef boost::property_map<GraphType, boost::vertex_index_t>::const_type indexMapType; indexMapType indexMap(get(boost::vertex_index, graph)); boost::vector_property_map<float, indexMapType> myMap(100, indexMap); but how would I then be able to, only having the graph object, get this map? That is, there was never any name, like "vertex_data" introduced in this case. Thanks, David

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was it created or opened when using boost::interprocess::shared_memory_object?
by Gehua Yang 26 Jan '12

26 Jan '12

Dear folks, I have been using Boost's Interprocess module for communication between several peer processes. In particular, I am using the shared_memory_object. As I was trying to create it with open_or_create_t flag (to ensure it finishes in an atomic operation), I cannot tell whether it was created or it was just opened. I would like to apply initialization when it was created but use its current information when it was opened. I hope there is a member function that can return this status. Best regards, Gehua Yang

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[BOOST USERS] [ BGL ] [GRAPH ] iterating through the vertices and edges of a filter graph
by srinivas boppu 26 Jan '12

26 Jan '12

Hello All, I need a small help in iterating through the vertices and edges of a filtered graph. Here is some sample code of the filtered graph. ( http://programmingexamples.net/wiki/CPP/Boost/BGL/FilteredGraph) ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- #include <iostream> #include <boost/graph/adjacency_list.hpp>#include <boost/array.hpp>#include <boost/graph/filtered_graph.hpp>#include <boost/graph/graph_utility.hpp> template <typename TGraph>struct vertex_id_filter{ bool operator()(const typename boost::graph_traits<TGraph>::vertex_descriptor& v) const { return 3 < v; // keep all vertx_descriptors greater than 3 }}; int main(){ using namespace boost; typedef adjacency_list<vecS, vecS, directedS, no_property, property<edge_weight_t, int> > Graph; typedef property_map<Graph, edge_weight_t>::type EdgeWeightMap; unsigned int numberOfVertices = 10; Graph g(numberOfVertices); for(unsigned int i = 0; i < numberOfVertices - 1; ++i) { add_edge(i, i+1, g); } std::cout << "Original graph:" << std::endl; boost::print_graph(g); vertex_id_filter<Graph> filter; filtered_graph<Graph, boost::keep_all, vertex_id_filter<Graph> > filteredGraph(g, boost::keep_all(), filter); // (graph, EdgePredicate, VertexPredicate) std::cout << "Filtered graph:" << std::endl; boost::print_graph(filteredGraph); return 0;} ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Here is my question. How do I iterate through the vertices and edges of "filteredGraph". I wanted to use the functions vertices( filteredGraph) and edges(filteredGraph) seems that we cannot use these functions as in the case of filtered graphs they return filtered_iterators. Please, can some one extend the above example and show me how to iterate through the vertices and edges. Thanks and Regards, Srinivas Boppu

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Ticket 4787 / Udp control headers.
by amit khandelwal 26 Jan '12

26 Jan '12

I was going through the 1.48 source code and I don't see it there. Is there a plan to add this patch or was it rejected due to some reason? Thanks, Amit Khandelwal

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boost filesystem
by John Emmas 26 Jan '12

26 Jan '12

Hello, I hope someone here will be able to help with this. Sorry, but the background is a little long-winded.... I've just discovered to my dismay that Microsoft's implementation of fstream, ifstream and ofstream are fatally flawed. I'm not sure if these characters will display correctly across this mailing list but consider the following character set:- ΔΗΜΗΤΡΗΣ which is apparently the Greek name "Dimitris". In an English locale, the following path would only be considered valid (by Windows) in a Unicode environment:- C:/Users/ΔΗΜΗΤΡΗΣ/some_file_name That's fine - because the user name doesn't contain valid English characters. However in Greece, that same path should qualify as a valid, non-Unicode file path and should therefore be openable without needing Unicode. For example, when building with MSVC this works:- #include <fcntl> int file = _open("C:/Users/ΔΗΜΗΤΡΗΣ/some_file_name", _O_RDONLY); However, this fails to work - even though it uses the same path:- #include <fstream> using std::fsrream; fstream file("C:/Users/ΔΗΜΗΤΡΗΣ/some_file_name", fstream::in | fstream::out); To cut a long story short, I noticed that libboost offers its own 'filesystem' implementation. Does boost::filesystem implement its own fstream, ifstream and ofstream? If so, would they likely suffer from the same problem (on Windows). If not, where can I find some examples of using boost::filesystem? Thanks, John

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[interval][units] interval operators not working when inteval elements are quantities
by alfC 26 Jan '12

26 Jan '12

Hi, Does anybody know what is missing in the boost.interval (or in the boost.units) to allow these operation. It seems that there is no other way than to make "interval/arith.hpp:operator/" more generic. -- Thanks, Alfredo #include<boost/units/systems/si.hpp> #include "alf/boost/units/interval.hpp" int main(){ boost::numeric::interval<double> iv(1.,10.); clog << iv << " " << 1./iv << endl; // ok, gives [1., 10] and [0.1,1.] boost::numeric::interval<quantity<si::length> > iv2(1.*si::meter, 10.*si::meter); clog << iv2 << " " << 1./iv2 << endl; // error: no match for ‘operator/’ in ‘1.0e+0 / iv2’ return 0; }

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FW: adjacency lists
by Neiderer, Andrew M CIV (US) 26 Jan '12

26 Jan '12

tried with https://svn.boost.org/svn/boost/trunk/boost/graph/adjacency_list_io.hpp but getting during translation. Thank you for your time. __________________________________________________________________________________________________________________________________________________________________________ > From: boost-users-bounces(a)lists.boost.org [boost-users-bounces(a)lists.boost.org] on behalf of Jeremiah Willcock [jewillco(a)osl.iu.edu] > Sent: Thursday, January 19, 2012 10:36 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] adjacency lists > > On Thu, 19 Jan 2012, Neiderer, Andrew M CIV (US) wrote: > > > > > This is about 1/4 of error message. I think if this is addressed then rest of errors will go away. > > > > > > > > Result of > > > > $g++ -I home/neiderer/src/C++/boost_1_48_0 -c adjacency_list_io.cpp > > > > > > > > (I do think you need src since already exists in .../libs/graph/example) > > Please try your code again with the change I just committed to the Boost > trunk (r76588). > > -- Jeremiah Willcock > > > > > > > > > Thank you > > > > ____________________________________________________________________________________________________________________ > > From: boost-users-bounces(a)lists.boost.org [boost-users-bounces(a)lists.boost.org] on behalf of Jeremiah Willcock > > [jewillco(a)osl.iu.edu] > > Sent: Thursday, January 19, 2012 9:27 AM > > To: boost-users(a)lists.boost.org > > Subject: Re: [Boost-users] adjacency lists > > > > On Thu, 19 Jan 2012, Neiderer, Andrew M CIV (US) wrote: > > > > > > > > I am still learning graphs, BGL 1.48.0 so beginner questions: > > > > > > > > > > > > 1. not sure what adjacency list/matrix are used for other than building a graph > > > > > > for traversal. Or maybe this is it? > > > > That is what they are used for -- to build and represent graphs. > > > > > > > > > > > > > > 2. I need to build a sparse network. So I am using adjacency_list_io.cpp by Francois Faure (2001). > > > > > > In this example I can read(g2), but when outputting > > > > > > > > > > > > std::cout << write(g2) > > > > > > > > > > > > I get lots of translation errors :-( > > > > > > > > > > > > I know I do not give details here but maybe someone could guess a -D??? to make > > > > > > adjacency_list_io.hpp happy. > > > > > > (The read(g2) works fine) > > > > > > > > > > > > Or I can certainly provide some of the error message. > > > > Could you please provide that? I am not familiar with that code. > > > > > > > > > > > > > > Also has Dr. Nick Edmonds completed (or near completion) of "active-message" based release (MPI)? > > > > We are still working on the paper based on that code. A release is likely > > to be within the next couple of months, but nothing is certain yet. > > > > -- Jeremiah Willcock > > > > > >

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[BGL] question about connected_components()
by Andriy Gapon 25 Jan '12

25 Jan '12

This page: http://www.boost.org/doc/libs/1_48_0/libs/graph/doc/connected_components.ht… says "The connected_components() functions compute the connected components of an _undirected_ graph using a DFS-based approach." [emphasis mine] Looking here: http://www.boost.org/doc/libs/1_48_0/boost/graph/connected_components.hpp I see somewhat some unexpected things. o Only the first variant asserts that the graph is undirected, in the second variant the assert is commented out - why is that? o Both variants use depth_first_search() and not undirected_dfs(), which would seem to be more logical for the undirected case - why? Despite the above questions I actually want to use connected_components() [and not strong_components()] for a directed graph. Should that be possible? Does it make sense? Thank you! -- Andriy Gapon

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d_ary_heap_indirect problem
by David Doria 25 Jan '12

25 Jan '12

I am trying to use d_ary_heap_indirect. I was able to create an object of the queue, but I can't push a vertex into it. Here is what I tried: http://programmingexamples.net/wiki/CPP/Boost/BGL/d_ary_heap_indirect I get a "no match for operator[]" error on the last line (the push()). Can anyone see what is wrong with that example? Thanks, David

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~optional<int> generates unnessesary code
by Hite, Christopher 25 Jan '12

25 Jan '12

The problem is that m_initialized is checked and set during deconstruction. This generates a bunch of useless code for types with trivial deconstruction: if(m_initialized){ // do nothing m_initialized = false; } The code is more than useless since it contains a branch. In my case I've got a big object I would expect to die without peep, branching and writing to memory for no reason. The steps below show what gcc 4.6.0 generates. You'd expect the function to do nothing. Boost optional has no obligation to maintain state during deconstruction (otherwise you'd need states for deconstructing,constructing). It's not responsible for the bytes left behind after deconstruction. By the way boost::variant does do this correctly. Chris ------------------ #include <boost/optional.hpp> typedef boost::optional<int> optional_int; void deconstruct_boost_optional(optional_int& o){ o.~optional_int(); } ------------------ objdump -f -d -C -l boost_optional_deconstruction.o |c++filt 00000000 <deconstruct_boost_optional(boost::optional<int>&)>: deconstruct_boost_optional(boost::optional<int>&)(): /home/eh2hite/chris/src_root/src/test/boost_optional_deconstruction.cpp:5 0: 8b 44 24 04 mov 0x4(%esp),%eax boost::optional_detail::optional_base<int>::destroy()(): /usr/local/include/boost/optional/optional.hpp:407 4: 80 38 00 cmpb $0x0,(%eax) 7: 74 03 je c <deconstruct_boost_optional(boost::optional<int>&)+0xc> boost::optional_detail::optional_base<int>::destroy_impl(mpl_::bool_<false>)(): /usr/local/include/boost/optional/optional.hpp:434 9: c6 00 00 movb $0x0,(%eax) c: f3 c3 repz ret

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