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

[Jed Brown]

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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