fortran interface for MatCreateSeqAIJWithArrays

[Barry Smith]

   Correct.
On Aug 24, 2009, at 4:42 PM, tsjb00 wrote:

> 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!
> > > 使用新一代 Windows Live Messenger 轻松交流和共享！ 立刻下载！
> >
>
> 搜索本应是快乐的，不是么? 快乐搜索，有问必应！微软隆 重推出! 立即试 
> 用！