You might want to consult the documentation for lamboot(1) and
mpirun(1), either in their respective man pages or in the LAM/MPI User
Guide.
You can certainly run four processes on one node (be aware that if you
only have 1 CPU that your four processes will be competing for CPU
time, so don't expect efficient results!). Without more detail, it's
difficult to know what your problem is. A wild guess would be that you
have hard-coded MPI_SEND and/or MPI_RECV calls in your application to
MPI_COMM_WORLD ranks greater than 0, but only ran one MPI process.
If you're trying to run 4 processes, you can be explicit with mpirun:
mpirun -np 4 your_app_name
Hope that helps.
On Oct 8, 2004, at 6:04 AM, ravin sachdeva wrote:
> hi ,
>
> i am working on a project that involves parallel processing so i
> obviously need to use lam...my project involves running a C source
> code on 4 processors with each processor exchanging info from one
> another using MPI_send and MPI_Recv calls... i was told that i can
> simulate a 4 processor environment using lam by setting the same
> hostname 4 times in the hostfile , then running lamboot on the
> processor and the code should work in parallel by giving the ranks
> 0,1,2,3 to the single processor...
> Here is where i am facing the problem.... the code only executes the
> rank 0's statements and halts when the MPI_Recv call by rank 0 is made
> giving the error:
>
> Rank(0,MPI_COMM_WORLD) : call stack for LAM
> Rank(0,MPI_COMM_WORLD) : MPI_Recv()
> Rank(0,MPI_COMM_WORLD) : main()
>
> and goes back to the shell. its not executing the other rank's(1,2,3)
> statements at all.
>
> is there anywhere that i am going wrong ?? what should i do ??
> please help ! you are my last hope.
>
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--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
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