fortran interface for MatCreateSeqAIJWithArrays

[tsjb00]

Many thanks for your reply! Just double check. So when I call MatCreateSeqAIJWithArrays from Fortran, I should define:
i(1)=0
j(1)=0
Correct?

Thanks again!

> From: bsmith at mcs.anl.gov
> To: petsc-users at mcs.anl.gov
> Subject: Re: fortran interface for MatCreateSeqAIJWithArrays
> Date: Mon, 24 Aug 2009 16:37:47 -0500
> 
> 
> On Aug 24, 2009, at 4:19 PM, tsjb00 wrote:
> 
> > Hi, there!
> >
> > I have a quick question on the Fortran interface of  
> > MatCreateSeqAIJWithArrays.
> >
> > The documentation indicates 'The i and j indices are 0 based'.
> 
>     This means the values in i and j start with zero; it does not mean  
> you have to declare them as PetscInt i(0:a big number) you can declare  
> them either as
> (0:a big number minus 1) or (1:a big number)
> 
> > Is it so when called in Fortran? Should the array be 0 based too?
> 
>     That does not matter.
> 
> > Any precautions to be taken to avoid segmentation error?
> 
>     This routine does NOT copy the values in the arrays. This means  
> that the arrays that YOU pass in, i,j,a must exist until you finish  
> using the matrix. If you allocate them
> then don't deallocate them until you destroy the matrix. If you  
> declare them, for example PetscScalar a(somebignumber) then make sure  
> this variable does not go out of
> scope until the matrix is destroyed.
> 
> >
> > Another question is about the storage of vector/arrays when using  
> > Fortran. In the PETSc examples, say a vector X_v is created using  
> > DACreateXXXVector, then the values are accessed with array X_a using  
> > DAVecGetArray. To access individual value, the loop is coded as:
> >     for (k=zs; k<zs+zm; k++) {
> >       for (j=ys; j<ys+ym; j++) {
> >     for (i=xs; i<xs+xm; i++) {
> >       for (idof=0;idof<dof;idof++){
> >                   X_a[k][j][i][idof]=.............
> > ...............................................
> > &nb sp;         }
> >         }
> >      }
> >  }
> > If in Fortran, how should the loop be structured? Please check if  
> > the following is right.
> >      do k=zs,zs+zm
> >      do j=ys,ys+ym
> >      do i=xs,xs+xm
> >      do iof=1,dof
> >            X_a(iof,i,j,k)=..............
> >       enddo
> > .............
> 
>     Yes.
> 
>     Barry
> 
> >
> >
> > Many thanks in advance!
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