- Boost-users - lists.boost.org

[BGL] - filtered_graph EdgePredicate performance
by Michael Fawcett 22 Jan '09

22 Jan '09

filtered_graph documentation says: [1] The reason for requiring Default Constructible in the EdgePredicate and VertexPredicate types is that these predicates are stored by-value (for performance reasons) in the filter iterator adaptor, and iterators are required to be Default Constructible by the C++ Standard. http://www.boost.org/doc/libs/1_37_0/libs/graph/doc/filtered_graph.html I only noticed this after scouring the documentation for hints as to why dijkstra_shortest_paths was taking 2 hours with a filtered_graph compared to 2 seconds with my adjacency_list. The reason for this huge difference was my filter's EdgePredicate had a boost::unordered_set member that returned true if the edge was in it. Changing that member to a pointer to an unordered_set reduced running time back down to the 2 second range. As I now understand it, every time a filtered graph iterator adaptor is incremented, it actually incrememts in a loop while the EdgePredicate returns false (or end is reached). This implies that the EdgePredicate should be extremely lightweight, since it is stored by-value in the iterator. What is the general recommendation when writing filter_graph predicates? My use case is filtering out all edges that reside inside a polygonal region. To do this, I do the intersection, then store the edges that are inside that region in an unordered_set. This requires that my EdgePredicate store a pointer to the graph and a pointer to the unordered_set since I can't hash an edge_descriptor without a reference to the graph (to get the target and source). That still seems big to me, given that it will be copied per iterator increment. On top of that, to ensure proper release of the unordered_set, I need to use shared_ptr or something similar, instead of just having the predicate own the unordered_set like it logically should, introducing yet more overhead in reference counting. The footnote states that it is stored by value for performance reasons. What types of predicate implementations were in mind when that was decided? I can't see a realistic filtering predicate that could say true/false with no member variables - at the very least it must store a pointer to the graph so that it can use the edge_descriptor. Is there a different, preferred way of writing EdgePredicates? Is there a way to get target/source from an edge_descriptor without the graph instance? Thanks, --Michael Fawcett

2 1

[GIL] Raw C pointer from any_image
by Olivier Tournaire 21 Jan '09

21 Jan '09

Hi all, I am wondering if it is posible to get a raw C pointer from an any_image / any_image_view. I tried this (taken from the tutorial): typedef boost::mpl::vector<gray8_image_t, rgb8_image_t> my_img_types; any_image<my_img_types> runtime_image; jpeg_read_image(filename.toStdString().c_str(), runtime_image); unsigned char* data = interleaved_view_get_raw_data( any_image_view<my_img_types>(runtime_image) ); And got the following errors: /usr/include/boost/gil/extension/io/../dynamic_image/../../image_view_factory.hpp:95: error: 'value' is not a member of 'boost::gil::view_is_mutable< .................. > error: no matching function for call to 'interleaved_view_get_raw_data(boost::gil::any_image_view< .................. > As I am really not familiar with the MPL, I am certainly doing something bad. Hope you could help. Regards, Olivier -- Olivier Tournaire MATIS - Institut Géographique National 73, Ave de Paris 94165 St Mandé cedex, France tel: (+33) 1 43 98 80 00 - 71 25 fax: (+33) 1 43 98 85 81

3 2

Pointer serialization
by niranjan bangera 21 Jan '09

21 Jan '09

hi am facing isssue in pointer serialization: version:1.36.0 linux : g++ 4.1.1 Where in sample ex shows; header file my.h contains: ------------------------- class second { int var1; float var2; template<class Archive> void serialize(Archive & ar, const unsigned int file_version) { ar & var1; ar & var2; } }; class first { second so; template<class Archive> void serialize(Archive & ar, const unsigned int file_version) { ar & so; } }; mymain.cpp ---------- #include "my.h" first *ptr; { std::ofstream ofs("filename"); boost::archive::text_oarchive oa(ofs); oa << ptr: } here in while compiling this(my.cpp) i am getting these errors -------------------------------------------------------------- /project_new/boost_1_36_0/include/boost-1_36/boost/archive/detail/oserializer.hpp:154: undefined reference to `boost::archive::detail::archive_pointer_oserializer<boost::archive::text_oarchive>::~archive_pointer_oserializer()' /project_new/boost_1_36_0/include/boost-1_36/boost/archive/detail/oserializer.hpp:154: undefined reference to `boost::archive::detail::archive_pointer_oserializer<boost::archive::text_oarchive>::~archive_pointer_oserializer()' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:76: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::extended_type_info_typeid_0()' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:78: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::type_register(std::type_info const&)' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:78: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::type_register(std::type_info const&)' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:78: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::type_register(std::type_info const&)' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:78: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::type_register(std::type_info const&)' /project_new/boost_1_36_0/include/boost-1_36/boost/serialization/extended_type_info_typeid.hpp:78: undefined reference to `boost::serialization::detail::extended_type_info_typeid_0::type_register(std::type_info const&)' ...................... /project_new/boost_1_36_0/include/boost-1_36/boost/archive/detail/oserializer.hpp:94: undefined reference to `boost::archive::detail::basic_oarchive::end_preamble()' /project_new/boost_1_36_0/include/boost-1_36/boost/archive/detail/oserializer.hpp:94: undefined reference to `boost::archive::detail::basic_oarchive::end_preamble()' /project_new/boost_1_36_0/include/boost-1_36/boost/archive/detail/oserializer.hpp:94: undefined reference to `boost::archive::detail::basic_oarchive::end_preamble()' Any suggestions will be accepted. Regards Niranjan

2 1

[Units] Can't assign equation
by Daniel Dilts 21 Jan '09

21 Jan '09

I'm using Boost.Units in a program for school to make certain that my equations are consistent (and that I didn't screw them up entering them). In the next Velocity equation, first get assigned with no problems, second causes a compiler error that I believe is saying that the constructor for quantity<velocity> is explicit. Why does first work without a conversion and second doesn't? Also, how do I get second to work? I assume this will require some type of explicit conversion, but wrapping the right-hand side with quantity<velocity>(...) doesn't work. const quantity<dimensionless> pi = 3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798; const quantity<time> deltaTime = .1 * second; const quantity<length> particleDiameter = .001 * meter; const quantity<dimensionless> dragCoefficient = 0.5; const quantity<dimensionless> specificGravityGold = 19.32; const quantity<acceleration> gravity = 9.80665 * meters_per_second_squared; const quantity<length> initialHeight = 0 * meters; const quantity<time> initialTime = 0 * seconds; const quantity<velocity> initialVelocity = root<2>(4.0/3 * specificGravityGold * gravity * particleDiameter / dragCoefficient); const quantity<mass_density> densityWater = 1000 * kilograms_per_cubic_meter; const quantity<mass_density> densityGold = 19300 * kilograms_per_cubic_meter; const quantity<mass> particleMass = 4.0 / 3.0 * pi * pow<3>(particleDiameter / 2.0) * densityGold; quantity<velocity> nextVelocity(quantity<velocity> old) { quantity<velocity> first = (pi / 6.0 * pow<3>(particleDiameter) * gravity * (densityWater - densityGold)) * deltaTime / particleMass; quantity<velocity> second = (pi / 8.0 * densityWater * dragCoefficient * old * root<2>(pow<2>(old))) * deltaTime / particleMass; ... }

2 1

Re: [Boost-users] behavior conditional on template argument
by Hicham Mouline 21 Jan '09

21 Jan '09

That is a beautiful trick. The sizeof trick basically. "C++ template metaprogramming" p212 As Joel says in that post, it should definitely be included in standard boost. Perhaps in the type traits library? thank you, > ----- Original Message ----- > From: "Igor R" <boost.lists(a)gmail.com> > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] behavior conditional on template argument > Date: Wed, 21 Jan 2009 13:17:56 +0200 > > > > > > You can use enable_if to let the compiler decide which one it should > > instantiate. And the argument will be a custom defined type trait. I > > think there are facilities to automatically define it on the presence > > of a type, there may be soemthing for fucntions as well, but I don't > > remember where they live (MPL ?) > > > Here it is: > http://www.nabble.com/compile-time-check-that-a-member-function-exists-td18… > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users >

2 1

Making Boost Portable with Our Code
by Gundala Viswanath 21 Jan '09

21 Jan '09

Dear all, I have a set of codes that use a lot of Boost tool. I then want to release the source code for public. Is there a way I can make port Boost in my code so that when people want to build/compile my code they don't need to have Boost install in there computer? - Gundala Viswanath Jakarta - Indonesia

2 1

Problem serializing a std::vector of a user-defined class containing a std::string
by Ivan Gonzalez 21 Jan '09

21 Jan '09

Dear all, I'm having problems to serialize a std::vector of a small class I use in my code. The class contains 3 members: a std::string, a size_t, and an another class passed as a template parameter (see the code below.) The class passed as a template is basically a std::map<int, blitz::Array<double, 2> >(see this post http://lists.boost.org/boost-users/2008/05/36282.php) I'm using the serialization library with the last class elsewhere in my code and works with no problems, so I guess the error must be in the code below. My program compiles and finishes OK, but the results I'm getting are slightly different from what I should get: it seems that somewhere in the serialization process the numbers stored in the third class get corrupted. I'm using boost 1.35, I need the binary file (I'm taking advantage of the serialization stuff for arrays contiguous in memory), and everything happens in the same machine in a single run of my code (so it is not a problem of different binary archives for different machines.) Thanks in advance, Ivan //-------------------------------------------------------------------------------------------- #include <iostream> #include <sstream> // for std::istringstream #include<boost/serialization/string.hpp> #include<boost/serialization/vector.hpp> #include<boost/archive/binary_oarchive.hpp> #include<boost/archive/binary_iarchive.hpp> template<class DataType> class ThingToStore{ public: typedef DataType data_type; ThingToStore() : site_(), name_(), data_() {} ThingToStore(const data_type& data, const std::string& name, int site) : site_(site), name_(name), data_(data) {} const std::string & name() const { return name_; } size_t site() const { return site_; } const data_type& map() const { return data_; } private: friend class boost::serialization::access; template<class Archive> inline void serialize(Archive& ar, const unsigned int file_version) { ar & BOOST_SERIALIZATION_NVP(site_); ar & BOOST_SERIALIZATION_NVP(name_); ar & data_; } size_t site_; std::string name_; data_type data_; }; template<class DataType> class StoredThingList { private: typedef std::vector<ThingToStore<DataType> > this_type; public: StoredThingList() {} template<class Index> void save(const Index& i, const std::string& name="blockOps_") const { // make a string for the name file std::ostringstream oss; oss<<i<<"_"<<".aux"; std::string s=name+oss.str(); // make a output stream to the file above and open it std::ofstream ofile(s, std::ios::binary); if ( ofile.is_open() ) { boost::archive::binary_oarchive oa(ofile); oa & (*this); } } template<class Index> void load(const Index& i, const std::string& name="blockOps_") { // make a string for the name file std::ostringstream oss; oss<<i<<"_"<<".aux"; std::string s=name+oss.str(); // make a input stream to the file above and open it std::ifstream ifile(s, std::ios::binary); if ( ifile.is_open() ) { vec_.clear(); boost::archive::binary_iarchive ia(ifile); ia & (*this); } } private: friend class boost::serialization::access; template<class Archive> inline void serialize(Archive& ar, const unsigned int version) { ar & vec_; } this_type vec_; }; //--------------------------------------------------------------------------------------------

2 1

boost geometry lib
by Andruit＠gmx.de 21 Jan '09

21 Jan '09

Hello, I am a newbie to boost and I have a question concerning the installation of additional libs. I am really interested in the geometry library (http://geometrylibrary.geodan.nl/ ) , but I don't know how to install it and compile my programs using that library. Has anybody done this before. Thanks in advance. Andreas -- Sensationsangebot verlängert: GMX FreeDSL - Telefonanschluss + DSL für nur 16,37 Euro/mtl.!* http://dsl.gmx.de/?ac=OM.AD.PD003K1308T4569a

3 2

Older boost releases
by Birju Prajapati 21 Jan '09

21 Jan '09

Hi, Is the only way to get an older boost release, i.e. 1.36, via subversion? I can't see any direct links on the site. If svn is the way, then is this the right directory to checkout v1.36? http://svn.boost.org/svn/boost/tags/release/Boost_1_36_0/ TIA, Birju Schneider Trading 4th Floor, 25 Copthall Avenue London EC2R 7BP -------------------------------------------------------- Message from: Birju.Prajapati(a)schneidertrading.com Message to: boost-users(a)lists.boost.org Attached files: 0 This e-mail and any files transmitted with it are confidential, may be legally privileged, and are for the sole use of the intended recipient. Copyright in this e-mail and any accompanying document created by us is owned by us. If you are not the intended recipient of this e-mail or any part of it please telephone our IT Department at the number shown above or by e-mail at info(a)schneidertrading.com. You should not use or disclose to any other person the contents of this e-mail or its attachments (if any), nor take copies. This e-mail is not a representation or warranty and is not intended nor should it be taken to create any legal relations, contractual or otherwise. Schneider Trading Associates Ltd (Registration No. 3692131) is incorporated in England and Wales and the registered office is at 25 Copthall Avenue, London EC2R 7BP. The company is authorised and regulated by the Financial Services Authority

6 5

behavior conditional on template argument
by Hicham Mouline 21 Jan '09

21 Jan '09

Hello, I have a template function template <typename M> void f(const M&) { // call M.f1() // call M.f2() // some Ms have a function f1Andf2() which does f1()+ f2() work faster // how can I write code that runs f1Andf2() if it's there // otherwise runs f1() then f2() } regards,

3 2