July 2006 - Boost-users - lists.preview.boost.org

When to use thread.join()
by Simon Reye 04 Jul '06

04 Jul '06

My apologies if this has been covered. I am new to boost and have been working with the boost thread class. I assume that the join() function waits for the thread to finish execution. But what if the thread has already finished executing? Can I still call join() and have it not wait for infinity? Simon

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[Spirit] puts namespace std into the global scope
by Johan Råde 04 Jul '06

04 Jul '06

It seems that the header boost/spirit.hpp puts the entire namespace std into the global scope. That is not very nice! --- Example 1 -------- #include <string> #include <sstream> #include <fstream> #include <vector> #include <boost/spirit.hpp> void f() { string s; istringstream iss; ofstream ofs; vector<int> v; } ---------------------- Example 1 should not compile (undefined symbols), but does compile. If the line #include <boost/spirit.hpp> is removed, then Example 1 does not compile. --- Example 2 -------- #include <boost/filesystem/path.hpp> #include <boost/filesystem/fstream.hpp> #include <boost/spirit.hpp> using boost::filesystem::path; using boost::filesystem::ifstream; void g() { path p; ifstream ifs(p); } ---------------------- Example 2 should compile but does not. The compiler complains that the symbol ifstream is ambigous. If the line #include <boost/spirit.hpp> is removed, then Example 2 does compile. I´m using Boost 1.33.1 and MSVC 7.1 on a Windows XP computer. --Johan Råde rade(a)maths.lth.se

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auto-diff expression templates-> MPL
by Russell L. Carter 03 Jul '06

03 Jul '06

Greetings, This is a beginner question about the MPL. I'm building a general purpose simulation program which will have an optimization module as well as an internal ODE solver which requires derivatives of the implemented algorithm in various forms. Around 1998-2002 there was a lot of enthusiasm for generating the derivatives automatically using expression templates. I'm not quite through with an exhaustive review of the literature but it appears the various efforts ran to ground on the compilation memory and cpu requirements that evaluating expression templates in their original form required. So 1st question, has anybody done something like this with mpl/fusion sequences and algorithms? Has there been an improvement in compile time performance? Do you have any pointers to trivial examples? I've read Alexandrescu, and Abrahams & Gurtovoy and it's not clear to me how to map the expression templates as described in the earlier efforts onto mpl sequences and algorithms. That's probably enough for now. Thanks for any help. Russell

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[shmem] and kernel 2.4 / linuxthreads
by Sascha Lumma 03 Jul '06

03 Jul '06

Hi all, I noticed that kernel 2.6 is a requirement for shmem on linux. Is it possible to get shmem to run - maybe with constraints - together with kernel 2.4 and the older pthread version (linuxthreads)? A start on a kernel 2.4 box produces a segmentation fault in shared_memory.hpp. To reach most users as possible, it would be nice to be compatible or if not possible to get as a minimum a normal termination. Sascha Lumma

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[BGL] python bindings build graph from edge list
by John Reid 03 Jul '06

03 Jul '06

Hi, I was trying to build a graph from an edge list and ran into some problems. The following code throws an exception on write_graphviz(). I think it is because there's no property map called node_id in the graph. import boost.graph as bgl edges = [ ( 'a', 'b' ), ( 'b', 'c' ), ( 'c', 'a' ) ] g = bgl.Graph( edges ) g.write_graphviz( 'bind-copy.dot' ) I get the following: Traceback (most recent call last): File "<stdin>", line 1, in ? KeyError: 'node_id' I couldn't manage to generate the node_id property map automatically. So after you have built the graph with the edge list constructor how do you know which vertex is which? I ended up using the following code to create the graph: def build( edges ): # Create a graph to build g = bgl.Graph() # Construct some property maps node_ids = g.vertex_properties[ 'node_id' ] = g.vertex_property_map( 'string' ) color = g.vertex_properties[ 'color' ] = g.vertex_property_map( 'string' ) centrality = g.vertex_properties[ 'centrality' ] = g.vertex_property_map( 'float' ) weight = g.edge_properties[ 'weight' ] = g.edge_property_map( 'float' ) length = g.edge_properties[ 'len' ] = g.edge_property_map( 'float' ) # create the edges and vertices name_2_vertex = { } for ( name1, name2 ) in edges: if not name_2_vertex.has_key( name1 ): v1 = name_2_vertex[ name1 ] = g.add_vertex() node_ids[ v1 ] = name1 else: v1 = name_2_vertex[ name1 ] if not name_2_vertex.has_key( name2 ): v2 = name_2_vertex[ name2 ] = g.add_vertex() node_ids[ v2 ] = name2 else: v2 = name_2_vertex[ name2 ] e = g.add_edge( v1, v2 ) weight[ e ] = 0.1 length[ e ] = 4 # Color articulation points red for v in bgl.biconnected_components( g ): color[ v ] = 'red' # Assign centrality values to property map bgl.brandes_betweenness_centrality( g, centrality ) return g This code seems to works fine. So I thought I'd post this just to see if I was missing something obvious and/or in the hope someone else might find it useful. Best, John.

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[BGL] All Possible Matchings
by Hossein Haeri 03 Jul '06

03 Jul '06

Dear all, I have a bipartite graph, and want to generate all its possible matchings. Any suggestions? TIA, --Hossein ___________________________________________________________ Yahoo! Messenger - with free PC-PC calling and photo sharing. http://uk.messenger.yahoo.com

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[BGL] Bipartite Graphs
by Hossein Haeri 03 Jul '06

03 Jul '06

Dear all, Any special facility there is in BGL for bipartite graphs? TIA, --Hossein ___________________________________________________________ All New Yahoo! Mail Tired of Vi@gr@! come-ons? Let our SpamGuard protect you. http://uk.docs.yahoo.com/nowyoucan.html

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[BGL]Customising the Adjacency List Storage
by Louis Lavery 03 Jul '06

03 Jul '06

According to the book [BGL p232], in order to customise the EdgeList I need to define a container generator and parallel edge traits class, and over load the push() and erase() functions for the custom container [BGL p234]. My custom container is user::PushBackList<T>... namespace user { template<typename ValueType> struct PushBackList { //... }; struct PushBackListS { }; } ...and I've put the (specialised) container_gen and parallel_edge_traits classes in namespace boost... namespace boost { template<typename ValueType> struct container_gen<user::PushBackListS,ValueType> { typedef user::PushBackList<ValueType> type; }; template<> struct parallel_edge_traits<user::PushBackListS> { typedef allow_parallel_edge_tag type; }; } ...now all I need do is overload the push() and erase() functions. The problem is they are in nested namespace graph_detail and are called with full qualification (i.e. boost::graph_detail::push(...)) from adjacency_list class. That means I need to put my overloads in boost::graph_detail. Is that right? Thanks, Louis.

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[BGL] Budled Properties
by Hossein Haeri 03 Jul '06

03 Jul '06

Dear BGL-ers, I'm so new to BGL, and a little mixed up about the properties. Is the "Six Degrees of Kevin Bacon" example in the documentation of 1.33.0 using Bundled Properties? Or, is it using that old style "using_adjacency_list.html" strongly recommended me to leave it? TIA, --Hossein ___________________________________________________________ All New Yahoo! Mail Tired of Vi@gr@! come-ons? Let our SpamGuard protect you. http://uk.docs.yahoo.com/nowyoucan.html

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Re: [Boost-users] Retrieve multindex value type?
by JOAQUIN LOPEZ MU?Z 03 Jul '06

03 Jul '06

----- Mensaje original ----- De: Francesco Biscani <bluescarni(a)gmail.com> Fecha: Domingo, Julio 2, 2006 6:19 pm Asunto: [Boost-users] Retrieve multindex value type? > Hello, > > is there a way to retrieve from a multiIndex container the type of > its content? > > I need to do something like this: > > template <class T> > class my_class > { > private: > T set; > > public: > void insert(const T::value_type &); <------ ? > }; > > Here T is a multiIndex container, and the insert function should > add a term to the set. Hence "insert" must accept as input the > kind of values that are stored in the multiIndex container. Is > there a way to do so or should I just add another parameter to > the template and use that as argument for insert? > Thanks, Hello Francesco, Indeed, multi_index_container provides a nested value_type typedef that you can use exactly in the way you describe. Have you encountered any problem in doing so? Thank you for using Boost.MultiIndex, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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