[petsc-users] VecSetSizes hangs in MPI

[Barry Smith]

> On Jan 4, 2017, at 4:21 PM, Manuel Valera <mvalera at mail.sdsu.edu> wrote:
> 
> Hello all, happy new year,
> 
> I'm working on parallelizing my code, it worked and provided some results when i just called more than one processor, but created artifacts because i didn't need one image of the whole program in each processor, conflicting with each other. 
> 
> Since the pressure solver is the main part i need in parallel im chosing mpi to run everything in root processor until its time to solve for pressure, at this point im trying to create a distributed vector using either 
> 
>      call VecCreateMPI(PETSC_COMM_WORLD,PETSC_DECIDE,nbdp,xp,ierr)
> or
>      call VecCreate(PETSC_COMM_WORLD,xp,ierr); CHKERRQ(ierr)
>      call VecSetType(xp,VECMPI,ierr)  
>      call VecSetSizes(xp,PETSC_DECIDE,nbdp,ierr); CHKERRQ(ierr)
> 
> 
> In both cases program hangs at this point, something it never happened on the naive way i described before. I've made sure the global size, nbdp, is the same in every processor. What can be wrong?

   How are you insuring that all processes are calling the VecCreateMPI()? My guess is that one process in MPI_COMM_WORLD is calling it and the other is not hence it is hanging waiting for that process.

   Run with two processes with option -start_in_debugger and two xterms should pop up, type cont in both, when it hangs wait a little while and then do control c in each terminal and type bt to see where each process is.

  Barry



> 
> Thanks for your kind help,
> 
> Manuel.