Re: [boost] Help needed with BGL & multi_index_container

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2005-01-30 08:34:49

Hi Alexander,

----- Mensaje original -----
De: Me here <rhjrjlbk2002_at_[hidden]>
Fecha: Viernes, Enero 28, 2005 5:21 pm
Asunto: [boost] Help needed with BGL & multi_index_container

> Hi there,
> 
> I need an advanced container which allows me to access
> my data over number of different indices. That is
> exactly what for boost::multi_index_container was
> made. But, my data items also have relationships with
> other data in the same container, which could be
> represented as directed graph.
> 
> So, I have made a custom container, which aggregates
> multi_index_container (MIC) to store data items and a
> graph (BGL) to store relationships. To allow switching
> from MIC to walk over relationships, as an additional
> field of my item in MIC I store BGL vertex; as vertex
> property in graph I store the key of unique index in
> MIC. So, MIC and BGL refer to each other. But, it is
> difficult to have those two containers in sync.
> 
> So, I made another attempt to have MIC as customized
> vertex storage. I succeed two write the code for it
> (see it below). It also compiles and links :-).
> Unfortunately, I can not add neither vertices not
> edges. If I try to add vertex as in commeted code
> below, an error errors that there is no convertion
> from vertex property to vertex descriptor (error
> message is below).
> 
> What's wrong?

Well, I'm no BGL expert, so take this with a grain of salt,
but I think adjacency_list does not work the way you're
assuming: it is adjacency_list that internally defines its
vertex_descriptor type, and uses the container supplied to
store them: so, you just cannot select what vertices actually
are (like it seems you're trying with ItemHolder.) In fact,
the primary API for adding vertices is

  add_vertex(g);

which does not specify the vertex being added (it is
created internally by adjacency_list). The syntax

  add_vertex(p,g);

is shorthand for adding a vertex and attaching it
a property.

I'd say that, in order to blend BGL with
multi_index_container, you have three options:

1. Maintain the two structures in sync, like you've done
in your first approach.
2. Use multi_index_container as a property map attached
to a graph. I don't know if this would work, since I'm
not a BGL conoisseur.
3. Create your own data structure modeling mutable graph
which internally uses multi_index_container. Besides
the multi-index container, you'll need another one for
storing edges, if you are to follow the way adjacency_list
works.

Good luck with your project,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

> 
> My another question is: how can I get access to my
> MIC stored in graph? I would like to use its indices.
> 
> Best wishes,
> Alexander
> 
> --------- sample code -----------
> #include <iostream>
> 
> #include <boost/multi_index_container.hpp>
> #include <boost/multi_index/ordered_index.hpp>
> 
> #include <boost/graph/adjacency_list.hpp>
> 
> using namespace boost;
> using namespace boost::multi_index;
> 
> using namespace std;
> 
> 
> struct MICSelector {};
> 
> struct Item
> {
>  Item(int _a=0, int _b=0, int _c=0)
>  : a(_a), b(_b), c(_c) {}
> 
>  int a,b,c;
> };
> 
> struct ItemHolder
> {
>  ItemHolder(int id=0, const Item item=Item())
>  : m_ID(id), m_item(item) {}
> 
>  int  m_ID;
>  Item m_item;
> };
> 
> struct ItemHolderKey
> {
>  typedef int result_type;
>  int operator()(const ItemHolder& v) const
>  { return v.m_ID; }
> };
> 
> template<class ValueType>
> struct MICWrapper
> {
>  typedef multi_index_container
>    <
>      ValueType,
>      indexed_by
>      <
>        ordered_unique< ItemHolderKey >
>      >
>    > type;
> };
> 
> namespace boost
> {
>  // the specialization for your selector
>  template<class ValueType>
>  struct container_gen<MICSelector, ValueType>
>  {
>    typedef typename MICWrapper<ValueType>::type type;
>  };
> 
>  template <>
>  struct parallel_edge_traits<MICSelector> {
>  typedef allow_parallel_edge_tag type;
>  };
> };
> 
> typedef adjacency_list
>    < listS, MICSelector,
>      bidirectionalS, ItemHolder
>    > MG;
> 
> int tmain(int argc, char* argv[])
> {
> 
>  MG mg;
> 
> /*
>  ItemHolder IH( 1, Item(1) );
> 
>  add_vertex( &IH, mg );
> 
> //  add_edge(
> //    ItemHolder( 1, Item(1) ),
> //    ItemHolder( 2, Item(2) ),
> //    mg );
> */
> 
>  cout << typeid(
> boost::graph_traits<MG>::vertex_descriptor ).name();
> 
>  return 0;
> }
> --------- sample code -----------
> 
> ----------- error message -------------
> Compiling...
> MIC_BGL.cpp
> c:\test\MIC_BGL.cpp(87) : error C2664:
> 'boost::add_vertex' : cannot convert parameter 1 from
> 'ItemHolder *__w64 ' to 'const
> 
boost::detail::adj_list_gen<Graph,VertexListS,OutEdgeListS,DirectedS,Ver
texProperty,EdgeProperty,GraphProperty,EdgeListS>::config::vertex_proper
ty_type
> &'
>  with
>  [
>   
> 
Graph=boost::adjacency_list<boost::listS,MICSelector,boost::bidirectiona
lS,ItemHolder>,
>    VertexListS=MICSelector,
>    OutEdgeListS=boost::listS,
>    DirectedS=boost::bidirectionalS,
>   
> 
VertexProperty=boost::detail::retag_property_list<boost::vertex_bundle_t
,ItemHolder>::type,
>   
> 
EdgeProperty=boost::detail::retag_property_list<boost::edge_bundle_t,boo
st::no_property>::type,
>    GraphProperty=boost::no_property,
>    EdgeListS=boost::listS
>  ]
>  Reason: cannot convert from 'ItemHolder *__w64 ' to
> 'const
> 
boost::detail::adj_list_gen<Graph,VertexListS,OutEdgeListS,DirectedS,Ver
texProperty,EdgeProperty,GraphProperty,EdgeListS>::config::vertex_proper
ty_type'
>  with
>  [
>   
> 
Graph=boost::adjacency_list<boost::listS,MICSelector,boost::bidirectiona
lS,ItemHolder>,
>    VertexListS=MICSelector,
>    OutEdgeListS=boost::listS,
>    DirectedS=boost::bidirectionalS,
>   
> 
VertexProperty=boost::detail::retag_property_list<boost::vertex_bundle_t
,ItemHolder>::type,
>   
> 
EdgeProperty=boost::detail::retag_property_list<boost::edge_bundle_t,boo
st::no_property>::type,
>    GraphProperty=boost::no_property,
>    EdgeListS=boost::listS
>  ]
>  No constructor could take the source type, or
> constructor overload resolution was ambiguous
> ----------- error message -------------
> 
> 
> 
>        	
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