[OMPI users] calling a parallel solver from sequential code

[Florian Bruckner]

hi,

how can i call an MPI parallelized solver routine from a sequential 
code. The sequential code is already existing and the structure looks 
like to following:

void main()
{
   do {
         x = rand();

         sequential_code(); // this sequential code should only be 
executed on the master node
         if (x == 2345) MPIsolve(); // this should be run in parallel
   } while(x == 1234);
}

i'm wondering how the call MPI-parallelized solver routine can be called 
without parallelizing the whole existing sequential code. at a certain 
point of the code-path of the sequential code, the parallel execution 
should be started, but how can this be achived.

when starting the application with mpirun there must be some code 
running on each node. and the same code-path needs to be followed by 
each process. But this would mean that exactly the same sequential code 
needs to be executed on each node!?

what am i missing?
thanks in advance
Florian