[petsc-users] Fortran initialization and XXXDestroy

[Satish Balay]

I think the current code is to support:

if (var not initialized): crate(var).

And there might be some mapping of 0 to NULL or some other state (hence the choice of -2)

Satish

On Tue, 2 Feb 2021, Barry Smith wrote:

> 
>   I cannot remember why I selected -2 as the initial value for PETSc objects in Fortran. Probably because it would ensure a dramatic crash if you used 
> an object without initializing it from Fortran.
> 
>   It could be changing 
> 
> config/BuildSystem/config/compilersFortran.py:      self.addDefine('FORTRAN_TYPE_INITIALIZE', ' = -2') 
> 
> to 0 would mean that if you called destroy on the object and never created it everything would be fine; so you would not need to use any special code to check.
> 
> Would that be a better model?
> 
>   Barry
> 
> 
> 
> > On Feb 2, 2021, at 2:34 PM, Mark Adams <mfadams at lbl.gov> wrote:
> > 
> > Thanks Randy, that makes sense.
> > Mark
> > 
> > On Tue, Feb 2, 2021 at 3:27 PM Randall Mackie <rlmackie862 at gmail.com <mailto:rlmackie862 at gmail.com>> wrote:
> > Hi Mark,
> > 
> > I don’t know what the XGC code is, but the way I do this in my Fortran code is that I initialize all objects I later want to destroy, for example:
> > 
> > mat11=PETSC_NULL_MAT
> > vec1=PETSC_NULL_VEC
> > 
> > etc
> > 
> > Then I check and destroy like:
> > 
> > if (mat11 /= PETSC_NULL_MAT) call MatDestroy(mat11, ierr)
> > 
> > etc.
> > 
> > Hope this helps,
> > 
> > Randy
> > 
> > 
> > > On Feb 2, 2021, at 12:17 PM, Mark Adams <mfadams at lbl.gov <mailto:mfadams at lbl.gov>> wrote:
> > > 
> > > Satish, a few years ago you helped us transition the XGC Fortran code from v3.7.7 and we seemed to have regressed.
> > > 
> > > As I recall we removed the initialization of Mats (for example) in XGC. PETSc seems to initialize them with -2 in Fortran (Albert, cc'ed, verified this today) and I recall that from our previous conversation. As I look at the code now Fortran MatDestroy just goes straight to C, which would explain our crashes when we MatDestroy an uninitialized (-2) Mat.
> > > 
> > > What is the correct way to delete with initializing Fortran objects?
> > > 
> > > Thanks,
> > > Mark
> > > 
> > > 
> > 
> 
>