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

15 Dec 2009

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

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...
...
using namespace std;
using namespace 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;
}
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
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-- 
__________________________
Tobias Columbus
t.columbus@gmx.de
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