[petsc-users] valgrind errors.

[Jed Brown]

On Tue, 19 Jan 2010 12:56:30 -0500, "(Rebecca) Xuefei YUAN" <xy2102 at columbia.edu> wrote:
> Dear Jed,
> 
> I have one more question, what is the difference or how could I know  
> whether I need DAGetArray() or DAGetLocalVector()+DAVecGetArray() to  
> get my array?

You can use the former unless you need to use it when packed up in a
vector.

In a mulitlevel scheme, I would probably put something like this in my
FormFunction:

  DA da = (DA)dmmg->dm,eda;

  PetscObjectQuery((PetscObject)da,"ExtraDA",(PetscObject*)&eda);
  if (!eda) {
    // create eda based on the layout of da
    PetscObjectCompose((PetscObject)da,"ExtraDA",eda);
    DADestroy(eda); // give away ownership
  }
  DAGetArray(eda,PETSC_TRUE,&extrafield); // or FALSE if you don't need ghost values

  ...

  DARestoreArray(eda,PETSC_TRUE,&extrafield);


This way the memory is only allocated once, it will work with multiple
levels, and get cleaned up when you are done.

Jed