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

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):

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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@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 *To:* boost-users@lists.boost.org *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

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Hi,

In order to understand bundled properties better, I tried to compile

On Tuesday 15 December 2009 08:36:46 am List User wrote: the example given in the link below. the code is pasted here: it gives a segmentation violation...

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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;

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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.

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3. In the kevin-bacon2.cpp approach for adding new properties to

the graph, the vertex_properties are read as

...

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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?

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