[petsc-users] what kind of stuffs I forget to free?

[Fande Kong]

Jed,

Thanks,


On Thu, Mar 20, 2014 at 10:39 PM, Jed Brown <jed at jedbrown.org> wrote:

> Fande Kong <fd.kong at siat.ac.cn> writes:
>
> > /*
> >  * commproblem.cpp
> >  *
> >  *  Created on: Mar 20, 2014
> >  *      Author: fdkong
> >  */
> >
> > #include <petscsnes.h>
> > #include <petscdm.h>
> > #include <petsc-private/snesimpl.h>
> >
> > static char help[] = "Need helps.\n\n";
> >
> > #undef __FUNCT__
> > #define __FUNCT__ "main"
> > int main(int argc,char **argv)
> > {
> >    Vec               vec;
> >    MPI_Request       request;
> >    MPI_Status        status;
> >    PetscMPIInt       tag =123;
> >    MPI_Comm          comm;
> >    PetscMPIInt       rank, size;
> >    PetscInt           recv =10;
> >    PetscInt           send = 0;
> >    DM                 dm;
> >    PetscErrorCode    ierr;
> >
> >    PetscInitialize(&argc,&argv,(char *)0,help);
> >    comm =  PETSC_COMM_WORLD;
> >    ierr =  MPI_Comm_rank(comm, &rank);CHKERRQ(ierr);
> >    ierr =  MPI_Comm_size(comm, &size);CHKERRQ(ierr);
> >    // create an object
> >    ierr =  VecCreate(comm, &vec);CHKERRQ(ierr);
> >    // take a comm from that object
> >    comm =  ((PetscObject) vec)->comm;
> >    // if we set comm back to PETSC_COMM_WORLD, the code should work fine
> >    //comm =  PETSC_COMM_WORLD;
> >    // receive messages from rank 0
> >    if( rank!=0)
> >    {
> >         ierr = MPI_Irecv(&recv, 1, MPIU_INT, 0,tag, comm,
> &request);CHKERRQ(ierr);
> >    }
>
> You have to wait on this request.  MPI_Requests are not automatically
> collected at some point where you can prove that the operation has
> finished.  The Wait should return immediately, but you have to call it.
> Otherwise MPI holds a reference to the communicator and will not call
> the destructors.
>
> >    if(!rank)
> >    {
> >          //send messages to all others
> >          for(PetscMPIInt i =1; i<size;i++)
> >          {
> >                 ierr = MPI_Isend(&send, 1, MPIU_INT, i, tag,  comm,
> &request);CHKERRQ(ierr);
> >          }
> >    }
> >    // rank 0 doest not need to wait, it could continue to do other
> things.
>
> It *does* need to wait eventually.
>
> >    if(rank !=0)
> >    {
> >      ierr =  MPI_Waitall(1,&request, &status);CHKERRQ(ierr);
> >    }
> >    ierr = VecDestroy(&vec);CHKERRQ(ierr);
> >    ierr = PetscFinalize();CHKERRQ(ierr);
> > }
>
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