Re: [boost] [parameter] Boost.Graph program not responding at run-time

Subject: Re: [boost] [parameter] Boost.Graph program not responding at run-time
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-12-03 16:14:50

On Sat, 3 Dec 2011, Lorenzo Caminiti wrote:

> On Sat, Dec 3, 2011 at 3:16 PM, Jeremiah Willcock <jewillco_at_[hidden]> wrote:
>> On Sat, 3 Dec 2011, Lorenzo Caminiti wrote:
>>
>>> On Sat, Dec 3, 2011 at 2:28 PM, Jeremiah Willcock <jewillco_at_[hidden]>
>>> wrote:
>>>>
>>>> On Sat, 3 Dec 2011, Lorenzo Caminiti wrote:
>>>>>
>>>>> If I move the call to boost::depth_first_search into a template
>>>>> depth_first_search_impl and out of the Boost.Parameter function body,
>>>>> the code compiles (both MSVC and GCC with latest Boost from trunk) but
>>>>> the executable runs forever and prints nothing to cout... What am I
>>>>> doing wrong?
>>>>
>>>>
>>>> I tried your code with GCC 4.6.0 and it worked just fine as you pasted it
>>>> below.  I get:
>>>>
>>>> order of discovery: u v y x w z
>>>> order of finish: x y v u z w
>>>>
>>>> as the result.  You are returning an invalid pointer from
>>>> default_color_map(), though; &colors[0] becomes invalid when colors is
>>>> destroyed at the end of the function.
>>>
>>>
>>> Oops... thanks, that was actually the issue, after I fixed the invalid
>>> pointer the code runs fine.
>>>
>>> BTW, what's the best way to generate a default_color_map for
>>> Boost.Graph like the one below?
>>
>>
>> Probably the simplest is to use shared_array_property_map; you can return
>> those from functions as shallow copies.  If you write the default code in
>
> Something like this? But this gives me again the run-time error...
>
> template< typename Size, typename IndexMap >
> boost::iterator_property_map<boost::default_color_type*, IndexMap,
>        boost::default_color_type, boost::default_color_type&>
> default_color_map ( Size const& num_vertices, IndexMap const& index_map )
> {
>    boost::shared_array_property_map<boost::default_color_type,
>            IndexMap> colors(num_vertices, index_map);
>    return &colors[0];
> }

You don't return the iterator_property_map here; you return the 
shared_array_property_map itself as the result of the function.

-- Jeremiah Willcock