Hi Steve. Regarding Step 3, have you thought of using some shared storage? NFS shared drive perhaps, or there are many alternatives!
On 23 January 2016 at 20:47, Steve O'Hara <soh...@pivotal-solutions.co.uk> wrote: > Hi, > > > > I’m afraid I’m pretty new to both OpenFOAM and openMPI so please excuse me > if my questions are either stupid or badly framed. > > > > I’ve created a 10 Raspberry pi beowulf cluster for testing out MPI > concepts and see how they are harnessed in OpenFOAM. After a helluva lot > of hassle, I’ve got the thing running using OpneMPI to run a solver in > parallel. > > The problem I have is that if I switch the server node to not use the > cluster (still use 3 cores in an MPI job) the job finishes in x minutes. If > I tell it to use the 9 other members of the cluster, the same job takes x > times 3! > > > > This is what I’m doing; > > > > 1. Create a mesh, adjust it with some other OF stuff > > 2. Run the process to split the job into processes for each node > > 3. Copy the process directories to each of the affected nodes using > scp > > 4. Run mpirun with a hosts file > > 5. Re-constitute the case directory by copying back the processor > folders > > 6. Re-construct the case > > > > Only step 4 Uses MPI and the other steps have a reasonably linear response > time. > > Step 4 is characterised by a flurry of network activity, followed by all > the Pis lighting up with CPU activity followed a long time of no CPU > activity but huge network action. > > It’s this last bit that is consuming all the time – is this a tear-down > phase of MPI? > > Each of the Pi nodes is set up as slots=4 max_slots=4 > > > > What is all the network activity? It seems to happen after the solver has > completed its job so I’m guessing it has to be MPI. > > The network interface on the Pi is not a stellar performer so is there > anything I can do to minimise the network traffic? > > > > Thanks, > > Steve > > > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/01/28349.php >
