Re: [Boost-users] newbie - graph library - vertex properties

Subject: Re: [Boost-users] newbie - graph library - vertex properties
From: Suresh Kumar (suresh.amritapuri_at_[hidden])
Date: 2009-12-17 03:48:35

Thanks Tobias,
with warm regards
suresh

On Thu, Dec 17, 2009 at 12:13 AM, Tobias Columbus <t.columbus_at_[hidden]> wrote:
> Hi Suresh,
>
> One advantage I can think of, is the following:
> Suppose you're developing in a team and after some while you realize
> that your graph needs property XY. Then you don't have to mess around
> in some header file to adapt your team's graph classes, but you only
> have to adapt your code locally, initialize a property_map in your
> algorithm, use it and destroy it afterwards.
>
> Another scenario would be that a graph is passed through some kind of
> pipeline and each pipeline step only needs to use local property_maps
> that saves memory, as the graph doesn't need to have internal all
> properties.
>
> Finally I think the reason that property_maps are used in boost, is
> that they make generic programming much easier, as the library
> programmer doesn't fix the implementation of some property but the
> library user may choose the adequate property_map for his/her code.
>
> Regards
> Tobias
>
> On Thursday 17 December 2009 06:54:17 am Suresh Kumar wrote:
>> Hi Tobias
>>
>> I managed to figure out how to use the property maps. When we can get
>> vertex property as graph[vertex_descriptor] why property maps? again,
>> when the above method is available, what do we gain by vertex_bundle
>> property tag etc?
>>
>> Thanks
>> suresh
>>
>> On Wed, Dec 16, 2009 at 5:00 PM, Suresh Kumar
>> <suresh.amritapuri_at_[hidden]> wrote:
>> > Hi,
>> >
>> > For example, I wrote the following:
>> >  typedef property_map<Map, double Highway::*>::const_type IndexMap;
>> >  IndexMap index = get(&Highway::miles,map);
>> >
>> > But I am unable to figure out how to get the actual vertex property
>> > from the IndexMap index.
>> >
>> > Also, how do we use, get(vertex_bundle, map)?
>> >
>> > Thanks
>> > suresh
>> >
>> >
>> > On Wed, Dec 16, 2009 at 4:09 PM, Suresh Kumar
>> > <suresh.amritapuri_at_[hidden]> wrote:
>> >> Hi Tobias,
>> >>
>> >> Can you just show, how to access the vertex properties using the
> get()
>> >>  function?. I know that map[vertex_descriptior] gives me the
>> >> vertex_properties of that particular vertex. But I am unable to
> figure
>> >> out how to use the get function for single vertex property as well
> as
>> >> for the vertex_bundle,
>> >>
>> >> Thanks
>> >> suresh
>> >>
>> >> On Tue, Dec 15, 2009 at 3:18 PM, Tobias Columbus
> <t.columbus_at_[hidden]> wrote:
>> >>> Hi again,
>> >>>
>> >>> Try the following code, which just compiles fine with g++ 4.4.1 on
> my
>> >>> system:
>> >>>
>> >>> struct City{...};
>> >>> struct Highway{...};
>> >>>
>> >>> typedef ... Map;
>> >>>
>> >>> int main(){
>> >>> Map map;
>> >>> Map::vertex_descriptor v = add_vertex( map );
>> >>> Map::vertex_descriptor u = add_vertex( map );
>> >>> map[v].name = "Troy";
>> >>> map[v].population = 49170;
>> >>> map[v].zipcodes.push_back(12180);
>> >>> Map::edge_descriptor e = add_edge( u, 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;
>> >>> return 0;
>> >>> }
>> >>>
>> >>> Generally I would suggest reading
>> >>>
> http://www.boost.org/doc/libs/1_41_0/libs/graph/doc/quick_tour.html
>> >>> which gives a quick overview of how to handle graphs in BGL.
>> >>>
>> >>> If you work through this tutorial, vertex and edge properties
> will also
>> >>> get explained.
>> >>>
>> >>> Regards
>> >>> Tobias
>> >>>
>> >>> On Tuesday 15 December 2009 05:00:01 pm 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
>> >>>>
>> >>>>
>> >>> _______________________________________________
>> >>> Boost-users mailing list
>> >>> Boost-users_at_[hidden]
>> >>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>> >>>
>> >>
>> >>
>> >>
>> >> --
>> >> R. Suresh Kumar
>> >> PhD Student, Vislab
>> >> #216, Engineering II Bldg
>> >> University of California, Riverside,
>> >> CA 92521
>> >>
>> >
>> >
>> >
>> > --
>> > R. Suresh Kumar
>> > PhD Student, Vislab
>> > #216, Engineering II Bldg
>> > University of California, Riverside,
>> > CA 92521
>> >
>>
>>
>>
>> --
>> R. Suresh Kumar
>> PhD Student, Vislab
>> #216, Engineering II Bldg
>> University of California, Riverside,
>> CA 92521
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>
>
> --
> __________________________
> Tobias Columbus
> t.columbus_at_[hidden]
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>

-- 
R. Suresh Kumar
PhD Student, Vislab
#216, Engineering II Bldg
University of California, Riverside,
CA 92521