Re: [Boost-users] distributed breadth first search doesn't work properly?

Subject: Re: [Boost-users] distributed breadth first search doesn't work properly?
From: Cedric Laczny (cedric.laczny_at_[hidden])
Date: 2011-05-04 02:15:12

Hi,

I don't know if you are following on this actually, but the problem that you 
stated in December of last year kept puzzling me and I tried to get it cleared 
after all.
For a summary, you can look at http://groups.google.com/group/boost-
list/browse_thread/thread/273160db809f1702?fwc=2

Basically, what I understood so far is that the BFS-example seems to be 
"wrong" because the reduction operation (among others) is not appropriate.
However, it seems that it will be fixed soon.

Best,

Cedric

On Wednesday, 8. December 2010 10:49:54 Mattia Lambertini wrote:
> Hi, i am new to boost and i'm using the PBGL to write a software that
> compute some graph analysis. I've installed boost 1.44.0 and openmpi 1.5
> 
> I tried to run the breadth first search example located in
> $BOOST_ROOT/libs/graph_parallel/example
> 
> with the graph $BOOST_ROOT/libs/graph/test/weighted_graph.gr
> 
> 
> All went well since i figure out that the result is different if i run the
> algorithm with a different number of processors.
> Only with one processor the values are corrected.
> 
> here's what happens:
> 
> mpirun -np 1 ./breadth_first_search.out
> 
> graph g {
>   subgraph cluster_0 {
>     label="p0";
>     n0[label=0];
>     n1[label=2];
>     n2[label=1];
>     n3[label=2];
>     n4[label=1];
>   }
> 
>   n0 -- n2;
>   n1 -- n1;
>   n1 -- n3;
>   n1 -- n4;
>   n2 -- n1;
>   n2 -- n3;
>   n3 -- n4;
>   n4 -- n0;
>   n4 -- n1;
> }
> 
> ---------------------
> 
> mpirun -np 2 ./breadth_first_search.out
> 
> graph g {
>   subgraph cluster_0 {
>     label="p0";
>     n0[label=0];
>     n1[label=1];
>     n2[label=1];
>   }
> 
>   n0 -- n2;
>   n1 -- n1;
>   n1 -- n3;
>   n1 -- n4;
>   n2 -- n1;
>   n2 -- n3;
> 
>   subgraph cluster_1 {
>     label="p1";
>     n3[label=1];
>     n4[label=0];
>   }
> 
>   n3 -- n4;
>   n4 -- n0;
>   n4 -- n1;
> }
> 
> Is that correct?
> 
> >From the doc i can't figure out why..