[petsc-users] question of a Brazilian student about the use of "PETSC" in a cluster

[Barry Smith]

> Marcelo,

    There is something wrong with the PETSc install. Are you absolutely sure that PETSc was ./configure with the same MPI as as the mpirun that you use to launch the program?

    You can send configure.log to petsc-maint at mcs.anl.gov if you cannot figure it out on your own.

   Barry


On Dec 13, 2012, at 4:55 AM, Marcelo Guterres <m.guterres at gmail.com> wrote:

> Hello,
> 
> My name is Marcelo Guterres and I am PhD student in Brazil.
> 
> I use the PETSC in a cluster with 11 computers, each with 8 processors "Xeon 2.8GHz", "16GB RAM" and "4 HD SAS" from "146GB".
> 
> My question is about the PETSc following functions:
> 
>     -> Ierr = MPI_Comm_rank (MPI_COMM_WORLD, & rank); CHKERRQ (ierr);
>     -> Ierr = MPI_Comm_size (MPI_COMM_WORLD, & size); CHKERRQ (ierr);
> 
> 
> For example, using only MPI:
> 
> ----------------------------------------------------------------------------------------------
> 
> // Program hello word using MPI
> 
> #include <iostream>
> using namespace std;
> #include <mpi.h>
> 
> int main(int argc, char *argv[])
> 
> {
>    int size, rank;
>    MPI_Init(&argc, &argv);
>    MPI_Comm_size(MPI_COMM_WORLD,&size);
>    MPI_Comm_rank(MPI_COMM_WORLD,&rank);
>    
>    cout << "hello. I am process " << rank << " of " << size << endl;
> 
>    if ( rank == 0)
>    {
>        cout << "\nFinish !!" << endl;
>    }
> 
>    MPI_Finalize();
> }
> 
> 
> 
> ****  running the command has the following output:
> 
> [guterres at stratus hello]$ mpirun -np 3 ./hello
> 
> hello. I am process 1 of 3
> hello. I am process 0 of 3
> 
> Finish !!
> hello. I am process 2 of 3
> 
> 
> CONCLUSION: int size = 3;
> 
> ----------------------------------------------------------------------------------------------
> 
> 
> using only the PETSC
> 
> ----------------------------------------------------------------------------------------------
> 
> 
> static char help[] ="\n\n hello word PETSC !!";
> #include <iostream>
> #include <petscsys.h>
> using namespace std;
> 
> int main( int argc, char *argv[] )
> {
>    PetscErrorCode  ierr;
>    
>    PetscMPIInt  size, 
>                        rank;
>   
>    ierr = PetscInitialize(&argc,&argv,(char *)0,help);CHKERRQ(ierr);
>    ierr = MPI_Comm_rank(MPI_COMM_WORLD,&rank); CHKERRQ(ierr);
>    ierr = MPI_Comm_size(MPI_COMM_WORLD,&size); CHKERRQ(ierr);
> 
>    cout << "hello. I am process " << rank << " of " << size << endl;
>    
>    if ( rank == 0)
>    {
>        cout << "\nfinish !!" << endl;
>    }
> 
> 
>    ierr =  PetscFinalize( ); CHKERRQ(ierr);
>    return 0;
> }
> 
> 
> ****  running the command has the following output:
> 
> 
> [guterres at stratus hello_petsc]$ mpirun -np 3 ./hello
> 
> hello. I am process 0 of 1
> finish !!
> 
> hello. I am process 0 of 1
> finish !!
> 
> hello. I am process 0 of 1
> finish !!
> 
> 
> ----------------------------------------------------------------------------------------------
> 
> 
> MY QUESTION IS:
> 
> 
> THE OUTPUT OF THE PROGRAM WITH PETSC CORRECT???
> 
> the variable value PetscMPIInt  size = np ??
> 
> The correct output should not be:
> 
> 
> [guterres at stratus hello_petsc]$ mpirun -np 3 ./hello
> 
> hello. I am process 0 of 3
> 
> hello. I am process 1 of 3
> 
> hello. I am process 2 of 3
> 
> finish !!
> 
> CONCLUSION: PetscMPIInt size = 3 ??
> 
> 
> Thank you for your attention and excuse my writing in English.
> 
> 
> Marcelo Guterres