Re: [Boost-users] time out for r_c_shortest_paths

Subject: Re: [Boost-users] time out for r_c_shortest_paths
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2013-02-25 09:12:18

On Mon, 25 Feb 2013, Brammert Ottens wrote:

>
>
>> Hi,
>>
>> I want to be able to put a time out on the r_c_shortest_paths, and still
>> be able to get the optimal paths that have been found so far. Currently,
>> I changed the REF such that it always returns false as soon as the time
>> out has reach, in effect emptying the unprocessed_labels queue. The
>> problem with this is that the algorithm still needs quite some time to
>> actually empty the queue.
>>
>> I tried to have the on_label_popped(cur_label) throw an exception when
>> the timeout has been reached. The timeout itself works like a charm, but
>> because the pareto_optimal_solutions container is only filled after the
>> while loop I can't access the already found optimal solutions.
>
> You might want to have on_label_popped(l, g) take l by reference and set
> l.b_is_dominated to true.  You'll still need to empty the queue, but (if
> that approach works) it should be faster that way.
>
> -- Jeremiah Willcock
>
> Hi Jeremiah,
>
> Thanks for your suggestion, but if I understand correctly it would mean a change to the code. I do not want to change the code, because if ever there is an update to boost I just want to be able to replace the old libraries with the new ones. If I would change the code, I would keep the exception and put a try/catch statement around the while-loop. Then you go around the problem of having to empty the queue.
>
> Is there any change to get something like a graceful timeout supported in the boost graph algorithms?
>
> Brammert Ottens
>
> Hi,
>
> I've had a closer look and I was too quick in dismissing your solution. however, the on_label_popped(cur_label) gets a const reference to the label. I've used a const_cast to remove the const (see code below), but now the code crashes when cleaning up the labels using deallocate. Any ideas on what could be wrong?
>
> template<class Label, class Graph>
> void QRCSPPVisitor::on_label_popped( const Label& label, const Graph& graph )
> {
>  RCSPPVisitorData().IncrementLabelsPopped();
>
>  if ( TimedOut() || GetMillis(StartTime()) > MaxMillis() )
>  {
>    this->SetTimedOut();
>    const_cast<Label&>(label).b_is_dominated = true;
>  }
> }

I think you can just change the parameter declaration to be a non-const 
reference.  Can you please check where the crash occurs and whatever 
information you can get about the cause?  Thanks.

-- Jeremiah Willcock