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

Re: [Boost-users] Boost Graph Library: Shortest path problem
by Grégoire Dooms 07 Apr '06

07 Apr '06

> > Date: Fri, 07 Apr 2006 11:39:20 +0200 > From: Steven Van Ingelgem <steven.vaningelgem(a)dpd.be> > Subject: [Boost-users] Boost Graph Library: Shortest path problem > To: boost-users(a)lists.boost.org > Message-ID: > <D3D675A5A7892D4287068E36BAFABB91016EC6DD(a)dcexch2.dpdbe.com> > Content-Type: text/plain; charset=us-ascii > > Hi, > > > > I have a problem with using (actually with finding the correct function > for my problem) the BGL. > > What I have is 5000 cities (vertices), 14000 roads (edges) between them > (directional roads)... And what I want to know is which roads I have to > take to encounter the least cities on my way. > Simple answer: take no road at all ;-) > Every edge has a weight of 1... So the documentation points me to using > the breadth_first_search algorithm. > > But this function - as far as I can see - goes through the entire graph. > I don't see any way to stop it (for example when it has discovered my > targetcity)?? > Sorry about that, I did know you had a target city. If you want to stop at the target city, the short answer is : use a visitor and throw an exception. void breadth_first_search(const Graph& g, typename graph_traits<Graph>::vertex_descriptor s, Buffer& Q, BFSVisitor vis, ColorMap color); The BFSVisitor can be made with the make_bfs_visitor http://www.boost.org/libs/graph/doc/bfs_visitor.html pass it an eventlist made of a predecessor_recorder and a custom eventprocessor use breadth_first_search(g, s, Q, make_bfs_visitor(make_pair(record_predecessors(predecessor_map, on_tree_edge), my_eventvisitor(target_node)), colormap) with struct my_eventvisitor : public boost::base_visitor<my_eventvisitor>{ typedef boost::on_finish_vertex event_filter; Graph::vertex_descriptor target; my_eventvisitor(Graph::vertex_descriptor target): target(target) {} template <class Vertex, class Graph> void operator()(Vertex v, Graph& g) { if (v==target){ throw TargetDiscoveredException; } }; I did not try to compile this but it should be along the lines of what you are looking for. > Is it possible someone can point me where I can have a look at? > In short I need to calculate (a lot) of roads from different cities to > other cities (so it's not that I always have the same root vertex). > > If you have to compute the distance for nearly all pairs of cities, you might want to look for one of the all pairs shortest paths. Hope this helps, -- Gregoire Dooms

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Re: [Boost-users] Serialization: crash atlaunchofprogram(duetoboost::serialization::base_object)
by RIVASSEAU Jean Noel 07 Apr '06

07 Apr '06

Hi I've tried to set up a small example that can reproduce the problem, however I cannot seem to succeed... One thing is sure, the crash is due to the BSL and the base_object thing, because if I change this only thing, the program goes from running perfectly to crashing at launch. Note that it is not really a problem of a class having multiple parents (this could happen if for example you use multiple inheritance). It is a problem of a class "switching parents". Jean-Noël -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] De la part de Robert Ramey Envoyé : vendredi 7 avril 2006 06:25 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] Serialization: crash atlaunchofprogram(duetoboost::serialization::base_object) Note that there is a test test_..._mi which tests serialization with classes which have multiple parents. So I would hope that this wouldn't be a problem. But you never know Robert Ramey RIVASSEAU Jean Noel wrote: > Ok, I will try to send a small example to the list tomorrow. In fact > I think everything lies in the fact that using > boost::serialization::base_object also registers the fact that the > classes are parent and child. The serialization system needs to know > that in order to make casts later. > > Somehow it probably does not like it when it tries to register > several different classes as the parent of the same class. > > Jean-Noël

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Boost Graph Library: Shortest path problem
by Steven Van Ingelgem 07 Apr '06

07 Apr '06

Hi, I have a problem with using (actually with finding the correct function for my problem) the BGL. What I have is 5000 cities (vertices), 14000 roads (edges) between them (directional roads)... And what I want to know is which roads I have to take to encounter the least cities on my way. Every edge has a weight of 1... So the documentation points me to using the breadth_first_search algorithm. But this function - as far as I can see - goes through the entire graph. I don't see any way to stop it (for example when it has discovered my targetcity)?? Is it possible someone can point me where I can have a look at? In short I need to calculate (a lot) of roads from different cities to other cities (so it's not that I always have the same root vertex). Thanks for any suggestion! Steven Van Ingelgem

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[LAMBDA] calling a function pointer stored in a struct
by Imre 07 Apr '06

07 Apr '06

Hi I'm new to the boost::lambda lib, and have a problem. I have a list that stores struct objects. One field of the struct is a function pointer. I'd like to call the function pointer stored in each element of the list, but I can't get it right. First, I tried something like this: struct S { typedef void (*Func)(); Func f; ... }; ... std::list<S> l; ... for_each(l.begin(), l.end(), bind(&S::f, _1)); I think this doesn't work because the bind yields a function object that returns f itself, but doesn't call it. Instead, I'd need to build a function object that returns the result of calling the f stored in the current list node. Unfortunately, I don't know how to do it. Thanks for any help. Imre

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How to parse_config_file with blank key value?
by Matt England 07 Apr '06

07 Apr '06

Summary: Is it possible for the program_options parse-config-file capability to support a config file that has a "blank" keyword value as per this config file example: ---- cut here ---- username= password= ---- cut here ---- This file would be parsed as if there's no value set for these keys/parameters/settings. More background: I manage a development group that uses Boost, and our developers aren't sure how to do this, and I'm posting on their behalf. The answer is not obvious to me at: http://boost.org/doc/html/parse_config_file.html Are there other, pertinent docs? We want to do this to assist the users of our software to know which values *can* be set...without setting them in a default config file. -Matt

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Re: [Boost-users] Serialization: crash at launch ofprogram(duetoboost::serialization::base_object)
by RIVASSEAU Jean Noel 07 Apr '06

07 Apr '06

Ok, I will try to send a small example to the list tomorrow. In fact I think everything lies in the fact that using boost::serialization::base_object also registers the fact that the classes are parent and child. The serialization system needs to know that in order to make casts later. Somehow it probably does not like it when it tries to register several different classes as the parent of the same class. Jean-Noël -----Message d'origine----- De : boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] De la part de Robert Ramey Envoyé : jeudi 6 avril 2006 17:20 À : boost-users(a)lists.boost.org Objet : Re: [Boost-users] Serialization: crash at launch ofprogram(duetoboost::serialization::base_object) I would be wiling to look at a small example which demonstrates the problem. Robert Ramey RIVASSEAU Jean Noel wrote: > I have tried to use versioning. Exact same problem. > > More explanations: if I use the version facility, and at load I > switch the boost::serialization::base_object<MyBaseClass> depending > on the version, the same crash will happen. > > Eg: this code: > > if (version == 0) > { > boost::serialization::base_object<MyBaseClass_1> > } > Else > { > boost::serialization::base_object<MyBaseClass_2> > } > > Will cause the same crash. > > So, could you look at the code, because currently there is no way to > change the base class of an object appearing in serialized archives, > if you want to be able to read old archives. > > It seems like there is a bug, if the base_object is used several > times with different classes, the crash will appear. > > Thanks > > Jean-Noël > > > -----Message d'origine----- > De : boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] De la part de Robert > Ramey > Envoyé : mercredi 5 avril 2006 17:15 > À : boost-users(a)lists.boost.org > Objet : Re: [Boost-users] Serialization: crash at launch of program > (duetoboost::serialization::base_object) > > The "version" facility is provided for maintaining the ability to > read old > archives. It doesn't sound like you're using this and its sounds > like you > should be. > > Robert Ramey > > > "RIVASSEAU Jean Noel" <JN.RIVASSEAU(a)oberthurcs.com> wrote in message > news:87F60F7FA02FF749AFB02BD9FCAA6B0401074928@naserv31.nanterre.oberthurcs.com... > Hello, > > My program crashes at launch (not even a exit(0) as the first line of > main(int argc, char *argv[]) will stop it from crashing), due to the > BSL. > > What I am trying to do is: I have a class, whose serialization is > split (eg, > save and load functions are provided, and they are different). Now > this > class had a parent class, so I used to call > boost::serialization::base_object<MObject>() on the base class > MObject. > > However I want to change the parent of my class to a different class. > I also > want to update my old archives, so I decided to leave the load > function of > my class untouched, while I would change the save function, to update > the > call to base_object to the new parent class (not MObject anymore). I > thought > it would work, since it would load the old archive using the same > method, > but save it using the new, so I would have ran only one time the > program and > the archive would be updated (then, of course, before running it > again I > would have to recompile it one more time with the correct changes to > the > load function). > > But it does not work as expected, since it seems the BSL does not > like the > fact that save and load functions calls to > boost::serialization::base_object > do not specify the same base class. It does not complain at compile > time but > crashes at run time before even entering main and certainly before > loading > any archive. The crash is due to a NULL pointer, I have tried to > debug with > gdb but the crash apparently occurs on the _libkernel32_a_iname () so > I do > not not know where it is (too low level for me). > > Robert, do you have an idea what is going on? I suspect a bug - > however if > it is "normal" behaviour (I think it should then throw an exception > rather > than crash), > > *** > Tell that to the author of _libkernel32_a_iname () > > do you have an idea how could I update my archives? I need to change > the > parent of this class, but need to be able to read my old archives - > and > changing them "by hand" by looking into the XML archive code is tool > hard. > > Thank you, regards > > Jean-Noël Rivasseau > > > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users =

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iterator_adapter conversion to base iterator?
by Sebastian Weber 07 Apr '06

07 Apr '06

Hello everybody! Please don't blame for beeing foolish - I'm using the iterator-adapter class for the first time. I converted a standard iterator from a std::vector with the iterator_adapter stuff into another class random_set_iterator. But at certain points in my programm I need the random_set_iterator converted back to the original iterator class from the vector class. I noticed the base()-function which basically does the job, but I think there should be a more elegant and clearer way to do it. Am I wrong or shouldn't an adapted iterator almost always be convertible to it's base iterator? I'm sure, it should not hard to implement somthing like this, but how? Thanks in advance! Greetings, Sebastian

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I NEED HEMP PLEASEeeeeeeeeeeeeee
by Karim Bakir 06 Apr '06

06 Apr '06

I use multi array boost But I have problem : - I can't declare a multi array as a member variable , I have the error: unexpected "error C2321: syntax error : unexpected 'boost::extents" When I don' write the keyword "typdef" I have more mistakes. //Boost library #include <Boost/multi_array.hpp> #include <cassert> //Name Space using namespace std; using namespace boost; class MyClass { typedef boost::multi_array<double,2>array_type_2d; public: MyClass(); virtual ~MyClass(); array_type_2d M(boost::extents[10][10]); }; So I want to have : but I don't manage it. //myClass.h ////////////////////////// //Boost library #include <Boost/multi_array.hpp> #include <cassert> //Name Space using namespace std; using namespace boost; class myClass { boost::multi_array<double,2>array_type_2d; private : int dim1, dim2; array_type_2d MyMatrice(boost::extents[dim1][dim2]) ; array_type_2d MySecondMatrice(boost::extents[10][10]) ; }; //myClass.cpp //////////////////////////////// void myClass::tester() { for (int i= 0 ; i<dim1; +) for(int j=0;j<dim2;j++) MyMatrice[i][j] = 15; } for ( i= 0 ; i<10; +) for(int j=0;j<10;j++) MySecondMatrice[i][j] = 0; } Thankssss

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Please add support for Borland C++ Builder 2006
by Zhou Fan 06 Apr '06

06 Apr '06

Please add support for Borland C++ Builder 2006. I need it very much.

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signal type declaration problem
by Emre Birol 06 Apr '06

06 Apr '06

Hi all, I have a class like below and I want to declare a signal type inside my class. Unfortunately when I do that MS VC80 complaints. Any help highly will be appreciated. template <typename T> class MyTask { public: // type definitions typedef enum { waiting, running, completed, failed } States; typedef boost::signal<void (States)> StatusChanged; typedef boost::signals::connection Connection; }; I get two warnings first then an error: Warning 1 warning C4512: 'boost::signals::detail::bound_objects_visitor' : assignment operator could not be generated c:\lib\boost\include\boost-1_33\boost\signals\trackable.hpp 185 Warning 2 warning C4346: 'boost::signal<void(lumentest::NITask<trait>::States)>::slot_function_type' : dependent name is not a type c:\projects\tesla-at-sti\src\lumentest\devices\nitask.hpp 124 Error 3 error C2061: syntax error : identifier 'slot_function_type' c:\projects\tesla-at-sti\src\lumentest\devices\nitask.hpp 124 if I replace 'States' with an int type then it works. I think compiler can't find out the type of States properly... I've also tried following declarations. None of them worked. typedef boost::signal<void (MyTask::States)> StatusChanged; typedef boost::signal<void (MyTask<T>::States)> StatusChanged; typedef boost::signal<void (typename MyTask::States)> StatusChanged; thanks, Emre

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