Re: [igraph] betweenness centrality -- negative and floating values?

[Yong Zou]

Good morning Tamas,

I wouldn't think it is because of the platforms or gcc. It is because
of whether it is 32bits or 64 bits.

We have made the following test: (For the network I sent to you.)
-- previously: 32 bits machine, openSuSE 10.3,
Maximum betweenness is   376506206757352.750000, vertex 5411
Minimum betweenness is   -55004389285247.281250, vertex 125

-- now, the results on 64 bits system:
Maximum betweenness is   3616914.907793, vertex 1785
Minimum betweenness is   -25946.467790, vertex 4156

The maximum BC from the new test sounds reasonable.

The problem remains:
Negative BC values.

Best,
Yong

On Thu, Jun 11, 2009 at 1:52 AM, Tamas Nepusz<address@hidden> wrote:
> Hi Yong,
>
> I tested your graph and it looks like the issue is platform-dependent; e.g.,
> it doesn't happen in openSuSE 11.1 (gcc 4.3.2, igraph 0.5.2), but I can
> reproduce it with OS X (gcc 4.0.1, igraph 0.5.2 and igraph 0.6). I suspect
> some kind of an internal overflow problem, but it takes more time to track
> down the bug than I expected. I filed a bug report on Launchpad; if you want
> to get notified when there's some progress, subscribe to the bug report
> here:
>
> https://bugs.launchpad.net/igraph/+bug/385747
>
> --
> Tamas