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[BGL] what is the "Power-Law Out Degree" algorithm?
by Rui Carvalho 08 Sep '05

08 Sep '05

Hi, What is the PLOD algorithm http://www.boost.org/libs/graph/doc/plod_generator.html My understanding is that this is NOT the Barabasi-Albert model. Could someone post a reference (paper/book) to the algorithm, please. Thanks, Rui

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[graph] king ordering: get rid of "comparison between signed and unsigned" warning
by Marco Morandini 08 Sep '05

08 Sep '05

This patch allows to get rid of the "comparison between signed and unsigned" warning, issued by gcc 3.4.4 at -Wall. I'm not sure of the correctness of the (int)Qptr->size() cast. Regards, Marco Morandini --- /home/marco/Programmi/boost_1_33_0/boost/graph/king_ordering.hpp 2005-09-06 19:20:56.000000000 +0200 +++ king_ordering.hpp 2005-09-08 13:55:10.000000000 +0200 @@ -63,7 +63,7 @@ //heap the vertices already there std::make_heap(rbegin, rend, boost::bind<bool>(comp, _2, _1)); - int i = 0; + typename Buffer::size_type i = 0; for(i = index_begin; i != Qptr->size(); ++i){ colors[get(vertex_map, (*Qptr)[i])] = 1; @@ -168,7 +168,7 @@ int parent_location = Qptr->size() - heap_parent_location; bool valid = (heap_parent_location != 0 && child_location > index_begin + offset && - parent_location < Qptr->size()); + parent_location < (int)Qptr->size()); while(valid && comp((*Qptr)[child_location], (*Qptr)[parent_location])){

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boost v1.33 on VS2005
by Oleg Smolsky 08 Sep '05

08 Sep '05

Hi all, just reporting that entire boost compiled on August CTP of VS2005 aka VC8. Best regards, Oleg.

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boost threads: threads priority
by Amit Itzkovich 07 Sep '05

07 Sep '05

Hi, I was looking into using boost threads. However, it seems there isn't anyway to change thread priorities. I need to use a high priority thread in order to perform time-critical midi processing under Windows XP and MacOSX. Did I miss something? Thanks, Amit

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compile-time mapping: a[1] --> a1 ?
by Steven Allmaras 07 Sep '05

07 Sep '05

I would like to do a compile-time mapping of an array accessor to a list of scalars as in the following class: class MyArray1 { public: double& operator[](int n) { ??? } private: double a0, a1, a2, a3 ; } ; int main() { MyArray1 x ; x[1] = 2. ; } I've left off all the extraneous stuff like constructors. I don't know how to write the MyArray1::operator[] so that it will evaluate to one of the data members at compile time; an if-test would correctly evaluate but might not be optimized away and run slowly. Is there some way to do the compile-time evaluation using the MPL? I looked thru the tutorial but did not find anything that looked like it would work. One possibility that I considered was the C preprocessor concatenation operator ##, #define PICKMEMBER(n) a##n double& operator[](int n) { PICKMEMBER(n) ; } Unfortunately, this will not work for expressions like x[i+1]. It probably has additional problems other than being quite distasteful. Obviously, this would all be easy if I just implemented the member data with an array, class MyArray2 { public: double& operator[](int n) { return data[n] ; } private: double data[4] ; } ; In fact, I did do so and everything works fine. The reason that I am trying to implement the list of scalars method is to see if there are any CPU timing differences for my application, which amounts to matrix-vector operations for small, dense vectors whose sizes are known at compile time. I have tried uBlas but was disappointed with the timing results (and yes, I did compile with -DNDEBUG). I've also looked at other packages such as tvmet (it did worse). I finally tried rolling my own vector and matrix classes with lazy evaluation of binary operators via Eckel's "Thinking in C++, Vol 2"; I also studied source for uBlas and tvmet. So far, I am able to beat uBlas on my choice of compilers/platforms, but I'm still not getting the consistent performance that I was hoping for. Why am I so interested in performance? Two reasons. First, if I can get consistently good performance (i.e. performance that is close to raw C or Fortran) for fairly straightforward operations, then I can be more confident that as I increase abstraction, performance will not deteriorate substantially. Second, I am evaluating C++ for applications that have been traditionally written in Fortran -- in my case, CFD codes for airflow simulation. Issues of modularity, extensibility, maintenance, and the fact that very few students are learning Fortran anymore may not be enough to convince my peers. I think I will also need to show that we will not experience a substantial performance hit with C++. Thanks in advance for any help. Steven Allmaras Boeing Commercial Airplanes

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Re: [Boost-users] boost\serialization expects 2 arguments - 3 provided with VC71 /MDd
by Guoxing Yang 07 Sep '05

07 Sep '05

Robert, I really like the boost serialization library. However, I am having a similar compiler error with VC71. I am trying to use the following code for all STL collections. template void LoadFromXml(const std::string &sXmlText, TValue &oValue) { std::istringstream oInStream(sXmlText); assert(oInStream.good()); boost::archive::xml_iarchive oIn(oInStream); oIn >> BOOST_SERIALIZATION_NVP(oValue); // restore from XML archive. } When the VC71 uses Multi-threaded Debug DLL (/MDd) setting, it generates the following compiler error: C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7 \include\boost\serialization\split_free.hpp(55) : error C2780: 'void boost::archive::load(Archive &,T &)' : expects 2 arguments - 3 provided C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7 \include\boost\archive\detail\iserializer.hpp(514) : see declaration of 'boost::archive::load' C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7 \include\boost\serialization\split_free.hpp(54) : while compiling class- template member function 'void boost::serialization::free_loader::invoke(Archive &,T &,const unsigned int)' with [ Archive=boost::archive::xml_iarchive, T=std::vector ] C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7 \include\boost\serialization\split_free.hpp(70) : see reference to class template instantiation 'boost::serialization::free_loader' being compiled with [ Archive=boost::archive::xml_iarchive, T=std::vector ] C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7 \include\boost\serialization\vector.hpp(79) : see reference to function template instantiation 'void boost::serialization::split_free>(Archive &,T &,const unsigned int)' being compiled with [ Archive=boost::archive::xml_iarchive, _Ty=int, T=std::vector ] Changing the setting to Multi-threaded Debug (/MTd), everything works well. I could not figure out why. Could you please help me? Thanks Yang

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Re: [Boost-users] compile-time mapping: a[1] --> a1 ?
by boost＠dalvander.com 07 Sep '05

07 Sep '05

>I would like to do a compile-time mapping of an array accessor to a list of > scalars as in the following class: Hi Steven, This is something I found floating on the net some time ago, perhaps it will give you some ideas: template <typename T> class Vector4 { typedef T Vector4<T>::* const vec[4]; static const vec v; public: T x, y, z, w; Vector4() : x(0), y(0), z(0), w(0) { } Vector4(T _x, T _y, T _z, T _w) : x(_x), y(_y), z(_z), w(_w) { } const T& operator[](size_t i) const { return this->*v[i]; } T& operator[](size_t i) { return this->*v[i]; } }; template <typename T> const typename Vector4<T>::vec Vector4<T>::v = { &Vector4<T>::x, &Vector4<T>::y, &Vector4<T>::z, &Vector4<T>::w }; template <typename T> class Matrix4 { typedef Vector4<T> Matrix4::* const mat[4]; static const mat a; public: Vector4<T> i, j, k, l; Matrix4() : i(), j(), k(), l() { } Matrix4(const Vector4<T>& _i, const Vector4<T>& _j, const Vector4<T>& _k, const Vector4<T>& _l) : i(_i), j(_j), k(_k), l(_l) { } const Vector4<T>& operator[](size_t i) const { return this->*a[i]; } Vector4<T>& operator[](size_t i) { return this->*a[i]; } }; template <typename T> const typename Matrix4<T>::mat Matrix4<T>::a = { &Matrix4<T>::i, &Matrix4<T>::j, &Matrix4<T>::k, &Matrix4<T>::l }; Cheers, Anders Dalvander

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Thread events
by Johan 't Hart 07 Sep '05

07 Sep '05

Hello, I'm quite a newbie in the boost world, and I read the documentation about boost::threads. Inthere I read that events were not included in boost because they were too error-phrone. That made me wonder how to do multithreading without events, for example, how do you make a thread wait for something to do without events? I don't know how to implement that with just mutexes. Can someone help me? Thanks in advance. Johan 't Hart -- -- Mijn Postvak In wordt beschermd door SPAMfighter 11616 spam-mails zijn er tot op heden geblokkeerd. Download de gratis www.SPAMfighter.com vandaag nog!

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Re: [Boost-users] [serialization, 1_33_0] Correct usage and implementation for serializable objects without default constructors
by Martin Proulx 07 Sep '05

07 Sep '05

> Hello, > > While using the latest release of boost, I've encountered a few > questions concerning the usage of the serialization library with > objects without default constructors. > > Here they are: > > 1-) How can we construct an instance of a serialized object that > doesn't have a default constructor? > > The only option I've figured out is to normally construct an object > with bogus values, then unserialize the real values while reading from > the archive. Example: > > X(0) val; // 0 being some bogus value. > inputStream >> val; // Overwrites all values within val; > > Is this the correct way to do things? > >> No.. But I think what you want can be found in the manual in >> section: If you specialize save/load construct data you will get what >> you want. Use construct in place inside of load construct data. >> Reference/Serializable/Concept/Pointers/Non-Default Constructors. > > 2-) How should we split the serialization between the class' > serialize member versus load/save_construct_data? > > My observations show that when un/serializing objects directly like > shown above, load/save_construct_data aren't needed, so the serialize > member has to handle everything. When serializing a vector<X>, > load/save_construct_data does get called, so we have to un/serialize > some members in those functions as well. At first glance, it seems > some members will have to be un/serialized for the second time within > load/save_construct_data. > > Is that correct? For a class to be correctly un/serializable for all > cases, load/save_construct_data must un/serialize members that are > already taken care of in the serialize member? > >> Nope. >> >> If his isn't simple, then there is something wrong. Check the code >> in test_non_default_ctor . If it still doesn't give you what you >> need, ask again. >> >> RObert Ramey > Hello, Let me rediscuss everything with the example of test_non_default_ctor.cpp at hand. In this example, we have a class A that doesn't have a default constructor. An int is needed by the constructor, which is stored in the i member variable. load/save_construct_data are used to un/serialize the i member, while the serialize member is used for all other members. Looking at this test, I see a couple of behaviors that puzzle me. -) Saving the 'a' instance in the save() function doesn't end up calling save_construct_data. This leaves a serialized version of A which lacks the 'i' member. This makes it impossible to fully restore the 'a' instance. It seems problematic to me that save_construct_data isn't called in this case. In my planned usage, I'd like to fully serialize all members, regardless if the objects are serialized directly or through pointers. I cannot see how to do this without serializing the members needed to reconstruct the object in both serialize and save_construct_data, even if some members will end up serialized twice when an object is stored through a pointer. What's the proper way to serialize all members of a class without a default constructor so that it gets fully serialized regardless how the objects are managed? -) When restoring the 'a' instance within load(), in order to restore it, we first create another 'a' instance (with a different constructor argument), then restore the other members within, leaving untouched the 'i' member. Assuming I'd like to be able to serialize and unserialize completely objects that do not have a default constructor, I'm wondering how I can fully restore an object that doesn't have a default constructor. I currently can only see a single way, and it is the way it's done in load() for the 'a' instance; that is to construct an object with possibly irrelevant constructor arguments, and then unserialize the object from the archive. This has the downside of fully constructing an object with temporary values that will get replaced when we unserialize the real values. I've looked for some other mechanism relying on a copy constructor and something along the lines of load_construct_data, but I haven't found any. Here again, what is the syntax of choice to fully restore an object that doesn't have a default constructor? Thanks! Martin -- Tel: (450) 681-1681, #271 ------------------------------------------------------------------------ OKIOK Enterprise and e-business security solutions Solutions de sécurité d'entreprise et d'affaires électronique Tel. : (450) 681.1681 http://www.okiok.com This e-mail message (including attachments, if any) is intended for the use of the individual or entity to which it is addressed and may contain information that is privileged, proprietary, confidential and exempt from disclosure. If you are not the intended recipient, you are notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender and erase this e-mail message immediately. Le présent message électronique (y compris les pièces qui y sont annexées, le cas échéant) s'adresse au destinataire indiqué et peut contenir des renseignements de caractère privé ou confidentiel. 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[BGL] filtered_graph and null_vertex()
by Tiago de Paula Peixoto 06 Sep '05

06 Sep '05

Hello. Is the function graph_traits<G>::null_vertex() defined for G = filtered_graph? When I try to compile the following simple program: -------------------------------------------------------------- #include <boost/graph/adjacency_list.hpp> #include <boost/graph/filtered_graph.hpp> using namespace boost; int main() { typedef adjacency_list<vecS> graph_t; typedef filtered_graph<graph_t,keep_all> f_graph_t; graph_traits<f_graph_t>::vertex_descriptor v = graph_traits<f_graph_t>::null_vertex(); return 0; } -------------------------------------------------------------- I get the following error with GCC 4.0.1 and boost 1.33.0: /usr/include/boost/graph/graph_traits.hpp: In static member function ‘static typename boost::graph_traits<G>::vertex_descriptor boost::graph_traits<G>::null_vertex() [with G = main()::f_graph_t]’: filtered_test.cc:10: instantiated from here /usr/include/boost/graph/graph_traits.hpp:49: error: ‘null_vertex’ is not a member of ‘main()::f_graph_t’ Shouldn't null_vertex() just be defined to return the null_vertex() for the underlying graph, since the vertex descriptors are the same? Do I miss something? -- Tiago de Paula Peixoto <tiago(a)forked.de>

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