[petsc-dev] MatCreateVecs from Fortran problem

[Satish Balay]

Ah - found it. So PETSc is doing this initialization for you.

config/BuildSystem/config/compilersFortran.py:    help.addArgument('Compilers', '-with-fortran-type-initialize=<bool>',   nargs.ArgBool(None, 1, 'Initialize PETSc objects in Fortran'))
config/BuildSystem/config/compilersFortran.py:      self.addDefine('FORTRAN_TYPE_INITIALIZE', ' = -2')
src/vec/f90-mod/petscvec.h:        PetscFortranAddr:: v PETSC_FORTRAN_TYPE_INITIALIZE

Satish

On Tue, 17 Mar 2020, Satish Balay wrote:

> The issue is:
> 
> C has:
> 
> Vec v=NULL;
> Vec *v=NULL;
> 
> However its not clear how to implement this with current f90 interface.
> 
> I think we currently have:
> 
> Vec v = PETSC_NULL_VEC = 0 => the second one.
> 
> What you are looking for is the first one. I see this is automatically
> set.  I don't see this initialization in petsc - so perhaps the
> compiler is doing this automatically? [atleast by gfortran]
> 
> Satish
> 
> -------------
> 
> Breakpoint 2, MAIN__ () at ex1f.F90:51
> 51            x = PETSC_NULL_VEC
> (gdb) list 33
> 28      !
> 29            Vec              x,b,u
> 30            Mat              A
> 31            KSP              ksp
> 32            PC               pc
> 33            PetscReal        norm,tol
> 34            PetscErrorCode   ierr
> 35            PetscInt i,n,col(3),its,i1,i2,i3
> 36            PetscBool  flg
> 37            PetscMPIInt size
> (gdb) p x
> $2 = ( v = -2 )
> (gdb) p b
> $3 = ( v = -2 )
> (gdb) p u
> $4 = ( v = -2 )
> (gdb) p A
> $5 = ( v = -2 )
> (gdb) p ksp
> $6 = ( v = -2 )
> (gdb) p pc
> $7 = ( v = -2 )
> (gdb) c
> Continuing.
> 
> Breakpoint 3, MAIN__ () at ex1f.F90:52
> 52            call MPI_Comm_size(PETSC_COMM_WORLD,size,ierr)
> (gdb) p x
> $8 = ( v = 0 )
> (gdb) 
> 
> 
> 
> On Tue, 17 Mar 2020, Mark Adams wrote:
> 
> > >
> > > Passing NULL to MatCreateVecs() means that you do not want a vector out:
> > >
> > >
> > Yes, I want both vectors out and we pass it Vec that have been initialized
> > with PETSC_NULL_VEC
> > 
> > 
> > >
> > > https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateVecs.html
> > >
> > > I am guessing that this was broken in 3.7 so that it ignored NULL input,
> > > but we fixed that.
> > >
> > >
> > v3.7 has these CHKFORTRANNULLOBJECT. Well the "fix" broke working code
> > 
> > ex73f90t does not initialize the "x" vector that it gives
> > to matcreatevecs_. Should we just remove initialization of our vectors to
> > PETSC_NUILL_VEC?
> > 
> > Is the PETSc model that you don't inialized PETSc object to NULL because
> > you check that pointers are valid PETSc pointers instead of testing on
> > NULL? So maybe we should remove all these initializations.
> > 
> > Thanks,
> > Mark
> > 
> > 
> > >   Thanks,
> > >
> > >     Matt
> > >
> > >
> > >> call MatCreateVecs(solver%KKTmat,solver%xVec2,solver%bVec2,ierr)
> > >>
> > >> Petsc code:
> > >> PETSC_EXTERN void PETSC_STDCALL matcreatevecs_(Mat *mat,Vec *right,Vec
> > >> *left, int *ierr)
> > >> {
> > >> PetscPrintf(PETSC_COMM_SELF,"ZZZ 1) matcreatevecs_ start right=%p
> > >> left=%p\n",right,left);
> > >>   CHKFORTRANNULLOBJECT(right);
> > >>   CHKFORTRANNULLOBJECT(left);
> > >> PetscPrintf(PETSC_COMM_SELF,"ZZZ 2) matcreatevecs_ start right=%p
> > >> left=%p\n",right,left);
> > >>   *ierr = MatCreateVecs(*mat,right,left);
> > >> }
> > >>
> > >> produces this:
> > >>
> > >> ZZZ 1) matcreatevecs_ start right=0x7fffffff3758 left=0x7fffffff3760
> > >> ZZZ 2) matcreatevecs_ start right=(nil) left=(nil)
> > >>
> > >> Shouldn't  this be?
> > >>
> > >> PETSC_EXTERN void PETSC_STDCALL matcreatevecs_(Mat *mat,Vec *right,Vec
> > >> *left, int *ierr)
> > >> {
> > >>   *ierr = MatCreateVecs(*mat,right,left);
> > >> }
> > >>
> > >>
> > >
> > > --
> > > What most experimenters take for granted before they begin their
> > > experiments is infinitely more interesting than any results to which their
> > > experiments lead.
> > > -- Norbert Wiener
> > >
> > > https://www.cse.buffalo.edu/~knepley/
> > > <http://www.cse.buffalo.edu/~knepley/>
> > >
> > 
> 
>