Subject: Re: [Boost-users] newbie - graph library - vertex properties
From: Geoff Hilton (geoff.hilton_at_[hidden])
Date: 2009-12-15 19:37:55
Hi Suresh,
That's a good start, now try adding a second vertex and joining them
together with the edge "e" of the sample code. Hint: add_edge. :)
The problem is caused by this bit here (notice the similarity):
> > Map::edge_descriptor e = *out_edges(v, map).first;
Geoff
List User wrote:
> Hi Tobias Columbus,
>
> In fact I had tried that also. But then I got a funny message while
> executing like this: Ubuntu 9.04, g++ 4.3.3
> //Map::vertex_descriptor v = *vertices(map).first;
> Map::vertex_descriptor v = add_vertex(map);
>
> suresh_at_suresh-laptop:~/C++$ ./a.out
> *** glibc detected *** ./a.out: free(): invalid pointer: 0x09f9c064 ***
> ======= Backtrace: =========
> /lib/tls/i686/cmov/libc.so.6[0xb7e6a604]
> /lib/tls/i686/cmov/libc.so.6(cfree+0x96)[0xb7e6c5b6]
> /usr/lib/libstdc++.so.6(_ZdlPv+0x21)[0xb804d231]
> ./a.out[0x8049e7d]
> ./a.out[0x8049ea7]
> .
> .
> .
>
> so what to do next?*
> suresh
>
> *
> *
> *
> *
> ------------------------------------------------------------------------
> *From:* Tobias Columbus <t.columbus_at_[hidden]>
> *To:* boost-users_at_[hidden]
> *Sent:* Tue, December 15, 2009 3:45:42 AM
> *Subject:* Re: [Boost-users] newbie - graph library - vertex properties
>
> Hi suresh,
>
> Actually in the example you gave, there is no vertex in Map.
> Therefore vertices( map ).first is an iterator pointing to the end of
> vertices( map ) and accessing this element results in a segmentation
> violation.
>
> You first need to add some vertices by
>
> Map::vertex_descriptor v = add_vertex( map );
>
> Then v is a vertex of your graph and you may assign properties to it:
>
> map[v].name = "Troy";
>
> Regards
> Tobias
>
> On Tuesday 15 December 2009 08:36:46 am List User wrote:
> > Hi,
> >
> > In order to understand bundled properties better, I tried to compile
> the example given in the link below. the code is pasted here: it gives
> a segmentation violation...
> >
> > using namespace std;
> > using namespac e boost;
> >
> > struct City
> > {
> > string name;
> > int population;
> > vector<int> zipcodes;
> > };
> >
> > struct Highway
> > {
> > string name;
> > double miles;
> > int speed_limit;
> > int lanes;
> > bool divided;
> > };
> >
> > typedef boost::adjacency_list< boost::listS, boost::vecS,
> boost::bidirectionalS,City, Highway> Map;
> >
> > int main(){
> >
> > Map map; // load the map
> > Map::vertex_descriptor v = *vertices(map).first;
> > map[v].name = "Troy";
> > map[v].population = 49170;
> > map[v].zipcodes.push_back(12180);
> > Map::edge_descriptor e = *out_edges(v, map).first;
> > map[e].name = "I-87";
> > map[e].miles = 10;
> > map[e].speed_limit = 65;
> > map[e].lanes = 4;
> > map[e].divided = true;< br>> }
> >
> > How do I add memory for vertices in the above example?
> >
> > suresh
> >
> >
> >
> >
> > That example uses bundled properties
> (http://www.boost.org/doc/libs/1_41_0/libs/graph/doc/bundles.html)
> which remove the need for the operations you named.
> >
> > > 3. In the kevin-bacon2.cpp approach for adding new properties to
> the graph, the vertex_properties are read as
> > > adjacency_list[vertex_descriptior]. How will have a read only
> access in such a case? When I use this in a function which is
> > > defined as const in c++, the compiler cribs :)
> >
> > A function defined as const, or taking the graph as const? What error
> do you get?
> >
> > -- Jeremiah Willcock
> > ___________________ ____________________________
> > Boost-users mailing list
> > Boost-users_at_[hidden] <mailto:Boost-users_at_[hidden]>
>> http://listarchives.boost.org/mailman/listinfo.cgi/boost-users
> >
> >
> >
> >
>
> --
> __________________________
> Tobias Columbus
> t.columbus_at_[hidden] <mailto:t.columbus_at_[hidden]>