June 2010 - Boost-users - lists.preview.boost.org

[phoenix][units] make boost.phoenix play well with boost.units
by alfC 16 Jul '10

16 Jul '10

I have and expression of type arg1*arg1 which is contained in a deduced type LambdaExp (more preciselly composite<multiplies_eval,vector<argument<0>, argument<0> >) when trying to see what is the phoenix-deduced return type when input is double typename LambdaExp::template result<basic_environment<double> >::type naturally, it gives 'double' (double*double) but when the input type is a boost::units::quantity typename LambdaExp::template result<basic_environment<quantity<si::length> > >::type it gives: error_cant_deduce_type (instread of the equivalent of quantity<si::area>, like in quantity<si::area> a = quantity<si::length>()*quantity<si::length>() ) this is strange since it seemed that Phoenix worked out of the box with Units. What is going on? How can we help Phoenix deduce the return type? Does Phoenix need this help, like Boost.Lambda does by means of boost/ units/lambda.hpp? Thank you, Alfredo

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Default weight map doesn't work for weighted grid graph in A-star search
by W.P. McNeill 16 Jul '10

16 Jul '10

I am trying to write a simple example of an a-star search over a 2-dimensional grid using the Boost Graph Library. The source is hosted here: http://github.com/wpm/Boost-Searchable-Grid-Example. My intent is for this to be a resource for other people writing a-star searches. I am seeing an error about a missing weight map when I try to compile the call to astar_search(). As far as I can tell, everything is in order. I hoping someone has insight into what I'm missing. My graph class is a rank-2 grid graph called weighted_grid defined like so: typedef grid_graph<2> weighted_grid; I have a simple map that returns a weight of zero for every edge. struct edge_weight_map { typedef float value_type; typedef float reference; typedef edge_descriptor key_type; typedef readable_property_map_tag category; reference operator[](key_type e) const { // All edges have a weight of zero. return 0; } }; I associate this map with the weighted_grid class by specializing property_map. template<> struct property_map<weighted_grid, edge_weight_t> { typedef edge_weight_map type; typedef edge_weight_map const_type; }; I've defined valid expression functions for this property map along with a Euclidean distance heuristic and a visitor that throws an exception when a goal vertex is reached. The complete source is viewable at the URL given above. With these definitions I can do concept checks on the ReadablePropertyMap, ReadablePropertyGraph, VertexListGraph, and AStarHeuristic concepts. I can instantiate a weighted_grid. I can get the edge weight map using get(edge_weight, g) and the vertex index map using get(vertex_index, g). I think I have written everything I need to do a-star search. However, the following call does not build: vertex_descriptor source = vertex(0, g), goal = vertex(3, g); astar_search(g, source, euclidean_heuristic(goal), visitor(astar_goal_visitor(goal)) ); I get a long error spew. The first relevant problem appears to be here: ... /opt/local/include/boost/graph/astar_search.hpp:350: instantiated from ‘void boost::detail::astar_dispatch1(VertexListGraph&, typename boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, CostMap, DistanceMap, WeightMap, IndexMap, ColorMap, const Params&) [with VertexListGraph = boost::grid_graph<2ul, size_t, size_t>, AStarHeuristic = boost::euclidean_heuristic, CostMap = boost::detail::error_property_not_found, DistanceMap = boost::detail::error_property_not_found, WeightMap = boost::edge_weight_map, IndexMap = boost::grid_graph_index_map<boost::grid_graph<2ul, size_t, size_t>, boost::array<size_t, 2ul>, size_t>, ColorMap = boost::detail::error_property_not_found, Params = boost::bgl_named_params<boost::astar_goal_visitor, boost::graph_visitor_t, boost::no_property>]’ /opt/local/include/boost/graph/astar_search.hpp:372: instantiated from ‘void boost::astar_search(VertexListGraph&, typename boost::graph_traits<G>::vertex_descriptor, AStarHeuristic, const boost::bgl_named_params<P, T, R>&) [with VertexListGraph = boost::weighted_grid, AStarHeuristic = boost::euclidean_heuristic, P = boost::astar_goal_visitor, T = boost::graph_visitor_t, R = boost::no_property]’ main.cpp:36: instantiated from here ... (Line 36 main.cpp is the last line of the astar_search call.) This error message seems to be telling me that the weight map property for edges is missing, but I think I have properly implemented the get(edge_weight, g) function the documentation says is used to create the default weight map. Any idea what I'm doing wrong? Thanks.

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[MPI] optimization for homogeneous clusters
by Riccardo Murri 09 Jul '10

09 Jul '10

Hello, The manual for Boost.MPI 1.43.0 states: "More optimizations are possible on homogeneous machines, by avoiding MPI_Pack/MPI_Unpack calls but using direct bitwise copy. This feature can be enabled by defining the macro BOOST_MPI_HOMOGENEOUS when building Boost.MPI and when building the application." What is the correct way of building Boost.MPI for homogeneous systems? Should I just uncomment the relevant line in boost/mpi/config.hpp, or is there another (and recommended) way through Jam files? Thank you very much in advance for any suggestion. Best regards, Riccardo -- Riccardo Murri, Hadlaubstr. 150, 8006 Zürich (CH)

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[Boost.Uuid] Passing UUIDs with MPI
by Didier Devaurs 06 Jul '10

06 Jul '10

Hello, I'm having troubles trying to pass a uuid with MPI routines. Since a uuid is serialized as a primitive type, I was expecting it could be declared as an MPI datatype using: BOOST_IS_MPI_DATATYPE(boost::uuids::uuid) and sent via MPI routines. I've written a short program to illustrate the problem. It compiles but produces a "segmentation fault" error when I'm trying to run it: #include <iostream> #include <boost/mpi.hpp> #include <boost/uuid/uuid.hpp> #include <boost/uuid/uuid_io.hpp> #include <boost/uuid/uuid_generators.hpp> #include <boost/uuid/uuid_serialize.hpp> BOOST_IS_MPI_DATATYPE(boost::uuids::uuid) int main() { boost::mpi::environment env; boost::mpi::communicator world; if (world.rank() == 0) { boost::uuids::uuid u; u = boost::uuids::random_generator()(); std::cout << "u = " << u << std::endl; world.send(1, 0, u); } else { boost::uuids::uuid v; world.recv(0, 0, v); std::cout << "v = " << v << std::endl; } return 0; } Does anybody have an idea whether passing uuids would be possible, and if yes what is wrong in my code? Thank you, Didier Devaurs

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Boost UUIDS: string generator is crashing
by Carla Strembicke 06 Jul '10

06 Jul '10

I am using the following in my program for proof of concept. ( This was extracted straight from the documentation) boost::uuids::string_generator gen; boost::uuids::uuid u1 = gen("{01234567-89ab-cdef-0123456789abcdef}"); crashing in : template <typename CharIterator> uuid operator()(CharIterator begin, CharIterator end) const crashing at : *it_byte = get_value(c) Is this a bug or am I doing something wrong. When I remove the dashes it seems to work...... CONFIDENTIAL INFORMATION NOTICE: The information contained in this e-mail is privileged, confidential and intended solely for the use of the addressee named above. If the reader of this e-mail is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this e-mail is strictly prohibited. If you received this in error, please contact the sender and destroy all copies of this e-mail. Thank you.

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[date_time] How to parse "5th" into day of month?
by Adam Nielsen 05 Jul '10

05 Jul '10

Hi all, I'm a bit stuck with the date_time module. I found a few examples (ironically from bug reports) since I couldn't find any on the Boost documentation site, as I am trying to parse a string in the format "Fri 5th March 2010, 05:01pm" into a boost::gregorian::date structure. Unfortunately I can't figure out how to get it to recognise "5th". It works fine if the day is two digits, but for a single digit it returns the error "Day of month value is out of range 1..31" My date string is "%a %e.. %B %Y" (not sure if the ".." is correct but it was the only way I could get it to ignore the "th" after the day - again, I couldn't find anything about doing that in the docs.) Does anyone know whether it's possible to parse a date with a single digit day in it? Some of the docs hint that it's possible and give sample dates in that format, but they don't include the matching format specifiers to use. Here is my code: std::string strDate = "Fri 5th March 2010, 05:01pm"; std::string format("%a %e.. %B %Y"); boost::date_time::format_date_parser<boost::gregorian::date, char> parser(format, std::locale("C")); boost::date_time::special_values_parser<boost::gregorian::date, char> svp; boost::gregorian::date d = parser.parse_date(strDate, format, svp); std::cout << "Converted date from \"" << strDate << "\" to " << d << std::endl; Any suggestions would be much appreciated, or pointers to the correct documentation because I'm having real trouble finding where this sort of thing is explained :-( Many thanks, Adam.

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Boost.MultiArray + Boost.Lambda woes
by anony 02 Jul '10

02 Jul '10

I have the following code: typedef boost::multi_array<float, 3> multi_array_typea; multi_array_typea hfa; multi_array_typea::extent_gen extentsa; hfa.resize(extentsa[a][b][c]); multi_array_typea::const_iterator p(std::max_element(hfa.begin(), hfa.end(), bll::bind(static_cast<float(*)(float)>(&std::abs), bll::_1))); Which fails to compile, interestingly: multi_array_typea::const_iterator p(std::max_element(hfa.begin(), hfa.end())); compiles ok. Can someone please come up with appropriate BLL magic to resolve this situation? It seems to me, I'd somehow have to dereference bll:_1.

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PropertyGraphConcept concept checking errors for an example implicit graph
by W.P. McNeill 01 Jul '10

01 Jul '10

I am writing a stripped-down implicit graph that I hope can be a useful template for others working with the Boost Graph library. The project is hosted at github. Excerpts from the source are in this email, and the full source is viewable online at http://github.com/wpm/Boost-Implicit-Graph-Example. I am currently getting errors from the concept checking code which I don't understand and am looking for suggestions as to what I am doing wrong. This is graph class. struct ImplicitRingGraph { ImplicitRingGraph(size_t n):n(n) {}; // Graph concept typedef size_t vertex_descriptor; typedef boost::undirected_tag directed_category; typedef boost::disallow_parallel_edge_tag edge_parallel_category; typedef boost::adjacency_graph_tag traversal_category; // AdjacencyGraph concept typedef RingAdjacencyIterator adjacency_iterator; // PropertyGraph concept typedef boost::edge_weight_t edge_property_type; // Additional types required by the concept-checking code. typedef std::pair<vertex_descriptor, vertex_descriptor> edge_descriptor; typedef size_t vertices_size_type; typedef size_t edges_size_type; typedef size_t degree_size_type; typedef void out_edge_iterator; typedef void in_edge_iterator; typedef void vertex_iterator; typedef void edge_iterator; // The number of vertices in the graph. size_t n; }; typedef boost::graph_traits<ImplicitRingGraph>::edge_descriptor Edge; I want the edges to have weights, so it models the PropertyGraph concept. The following functions implement the valid expressions. EdgeWeightMap get(boost::edge_weight_t, ImplicitRingGraph& g) { return EdgeWeightMap(); } EdgeWeight get(boost::edge_weight_t tag, ImplicitRingGraph& g, Edge e) { return get(tag, g)[e]; } (Definitions of Edge, EdgeWeight, and EdgeWeightMap are visible online. I also define an adjacency iterator that is not shown here.) I can write code that reads an edge weight. ImplicitRingGraph g(5); EdgeWeightMap m = get(boost::edge_weight, g); boost::graph_traits<ImplicitRingGraph>::edge_descriptor e(0, 1); EdgeWeight w = get(boost::edge_weight, g, e); However I get errors when I try to use the concept checking code. function_requires< PropertyGraphConcept<ImplicitRingGraph, Edge, edge_weight_t> >(); The full error printout is huge, but there appear to be three relevant problems. 1. graph_concepts.hpp:406: error: conversion from ‘EdgeWeightMap’ to non-scalar type ‘boost::typed_identity_property_map<size_t>’ requested The line in graph_concepts.hpp is Map pmap = get(Property(), g); inside the concept check for PropertyGraph. It looks to me like I have a function to handle this. I don't understand where boost::typed_identity_property_map<size_t> is coming from. 2. graph_concepts.hpp:408: error: no matching function for call to ‘put(boost::edge_weight_t, ImplicitRingGraph&, Edge&, size_t&)’ I didn't write any put() functions so I understand why I'm getting this. However, I would like the edge weights to be readable but not writeable (myEdgeWeightMap models a ReadablePropertyMap), and I can't figure out how to specify the read-only property in the graph defintion. 3. graph_concepts.hpp:390: error: no matching function for call to ‘get(boost::edge_weight_t, const ImplicitRingGraph&)’ graph_concepts.hpp:391: error: no matching function for call to ‘get(boost::edge_weight_t, const ImplicitRingGraph&, Edge&)’ Should I create functions identical to what I've already written, except with constant modifiers in front of the graph type? That feels like redundant source. Thanks for any help you can give. Hopefully, a completed version of this example would be a useful resource for other BGL developers.

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bitsets in ITL
by Amir Gonnen 01 Jul '10

01 Jul '10

I'm evaluating ITL (Interval Template Library which was recently accepted to boost) in order to represent sparse bitsets. In the current implementation the large_bitset class is given as an example with minimal functionality. Are there any plans to develop it into a fully featured bitset and make it a part of boost? It would be nice if it implemented the interface of dynamic_bitset, to ease the migration between dynamic_bitset and large_bitset. Amir

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[boost-users][unit-test-framework] Problem linking tests.
by Germán Diago 01 Jul '10

01 Jul '10

Hello all. I'm having a hard time trying to link a binary against libbost_unit_test_framework. I was developing some software in my laptop. This laptop has installed boost libraries from the repositories (it's boost-1.40 ubuntu 10.04). I had to pass this code to another computer, which hadn't boost installed, so I copied what I had in ubuntu from the repositories into my project, headers included. My project uses boost_system and boost_thread as well. Both machines are 64 bit machines with intel. But when compiling, I get this: td::char_traits<char> >::_M_extract<unsigned long>(unsigned long&)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::basic_ostream<char, std::char_traits<char> >::_M_insert<bool>(bool)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_istream<char, std::char_traits<char> >& std::basic_istream<char, std::char_traits<char> >::_M_extract<long>(long&)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::basic_ostream<char, std::char_traits<char> >::_M_insert<void const*>(void const*)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::ctype<char>::_M_widen_init() const(a)GLIBCXX_3.4.11' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_istream<char, std::char_traits<char> >& std::basic_istream<char, std::char_traits<char> >::_M_extract<unsigned int>(unsigned int&)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::basic_ostream<char, std::char_traits<char> >::_M_insert<unsigned long>(unsigned long)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `std::basic_istream<char, std::char_traits<char> >& std::basic_istream<char, std::char_traits<char> >::_M_extract<bool>(bool&)(a)GLIBCXX_3.4.9' /home/gdiago/clientserver/deps/boost-1.40/lib/libboost_unit_test_framework.so: undefined reference to `__longjmp_chk(a)GLIBC_2.11' I also tried to compile my code with version 3.4 of g++, which is installed in the machine with no luck, same errors. Can anyone tell me if this is solvable without recompiling boost in the target machine? I'm not the mantainer of that machine, so I can't install boost. Thanks in advance.

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