Re: [Boost-users] graph cut compilation error

Subject: Re: [Boost-users] graph cut compilation error
From: David Doria (daviddoria+boost_at_[hidden])
Date: 2009-09-09 11:54:39

On Wed, Sep 9, 2009 at 11:07 AM, Jeremiah Willcock <jewillco_at_[hidden]>wrote:

> On Wed, 9 Sep 2009, David Doria wrote:
>
>  Any clues as to what I've done wrong? Maybe a simple example like this
>> could be put on the kolmogorov documentation page?
>>
>
> Sorry to spam you with another email, but I tweaked your code so it works
> and attached the result.  I just changed the residual capacity to a double,
> added the necessary vertex properties (one problem you had was that you were
> passing your edge properties to the graph as vertex properties), changed the
> edge capacity setting to what I posted a few minutes ago, and changed the
> result of kolmogorov_max_flow to be converted to a double.  It all compiles
> now.
>
> -- Jeremiah Willcock
> ____

Jeremiah,

Rather than spam, I'd call it fantastic information! I really appreciate
your time.

Although it compiles, the code you sent seems to segfault on the kolmogorov
call. Maybe because we didn't specify a source and sink? Shouldn't it work
without specifying them, thought? There should be two different mincut
problems that can be solved - 1) the min cut on the entire graph and 2) the
min cut dividing a specified source and sink (or multiple sources and/or
sinks). Do you know how to do that/why it is segfaulting?

Some other questions:

1) So this line creates two vertices:
Graph g(2);

then since the V0->V1 edge already exists, the add_edge function doesn't add
another edge, it simply returns something like a pointer to the already
existing edge so that properties, can be assigned to it, correct?

2) Since add_edge(..).first is the actual edge, it is implied that this a
pair and hence a .second - what is stored in the .second?

3) Would I get the edge weight like this:?
double ew = get(edge_capacity, g, add_edge(0, 1, g).first);

We're almost there!

Thanks again,

David