OK. I am now use MatGetSubMatrix.My code is as follows
? PetscMalloc(n*sizeof(PetscInt),&indices);?
? for (j = 0; j < n; j++)
? {??
????? indices[j] = j;
? }
? ISCreateGeneral(PETSC_COMM_SELF,n,indices,&iy); // get all columns
?....
?? PetscMalloc(2*sizeof(PetscInt),&indices);?
??? indices[0] = i;
??? indices[1] = j;
??? ISCreateGeneral(PETSC_COMM_SELF,2,indices,&ix);???? // only get i,j rows
??? Mat ui,uj;
// I am not sure how to set the third parameter : how many "local " columns..
Since I want all columns, I set it to n
???? ierr = MatGetSubMatrix(U,ix,iy,n, MAT_INITIAL_MATRIX,&ui);CHKERRQ(ierr);
What I really hope is to
????
??? for (i = 0; i < n; i++)
{
????? ????????? PetscInt row = 0;
????????? MatGetValues(ui,1,&row,1,&i,&u_ik);
}
It does not work. I tried to change the n to PETSC_DECIDE, it still does not
work
So, I really doubt that whether I can get the entire row of the matrix.
BTW, the matrix is created as follows:
?MatCreateMPIDense(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,m,n,PETSC_NULL,&U)
THank you
--- 09?12?2????, Barry Smith <bsmith at mcs.anl.gov> ???
???: Barry Smith <bsmith at mcs.anl.gov>
??: Re: How to copy global data to local ?
???: "PETSc users list" <petsc-users at mcs.anl.gov>
??: 2009?12?2?,??,??1:46
???Don't know what MatGetSubMatrixRaw() is, but based on the calling sequence
you are asking for the ith row whatever that is, and n columns in the array
indices
???For MatGetSubMatrix() each process can ask for any rows it wants, but all
the processors have to ask for the same columns that are wanted.
???Barry
On Dec 1, 2009, at 9:59 PM, ming zhu wrote:
> Hi
> I tried MatGetSubMatrix() but I am a little confused by the column parameter.
> For example
> My matrix is U (m * n). I want to get i,j rows to local.
> my code is
>
> PetscInt* rowindex,colindex;
> PetscMalloc...
> for (k= 0; k < n; k++)
>? ? colindex[k] = k;
>
> rowindex[0] = i;
> rowindex[1] = j;
>
> MatGetSubMatrixRaw(U,1,&i,n,indices,n,MAT_INITIAL_MATRIX,&newmat);
>
> What I hope is newmat is 2 * n matrix. But I failed.
>
> Thank you
>
>
> --- 09?12?1????, Barry Smith <bsmith at mcs.anl.gov> ???
>
> ???: Barry Smith <bsmith at mcs.anl.gov>
> ??: Re: How to copy global data to local ?
> ???: "PETSc users list" <petsc-users at mcs.anl.gov>
> ??: 2009?12?1?,??,??10:35
>
>
>? ? You misunderstand the usage of MatGetSubMatrix(). Any process can request
>ANY row, including rows that are not originally owned by that process.
>
>? ? Barry
>
> On Dec 1, 2009, at 8:29 AM, ming zhu wrote:
>
> > It seems that MatGetSubMatrix() only get the local matrix for the
> > processor? If U is global(PETSC_COMM_WORLD), the local matrix may not store
> > the column or row I wanted. For example, if U is 4*4, and there are 4
> > processors, processors one has local matrix 2*2, but i need the third row,
> > Then,MatGetSubmatrix() may not work
> >
> > --- 09?12?1????, Barry Smith <bsmith at mcs.anl.gov> ???
> >
> > ???: Barry Smith <bsmith at mcs.anl.gov>
> > ??: Re: How to copy global data to local ?
> > ???: "PETSc users list" <petsc-users at mcs.anl.gov>
> > ??: 2009?12?1?,??,??10:23
> >
> >
> > On Nov 30, 2009, at 11:21 PM, ming zhu wrote:
> >
> > > Hi
> > > I have a huge matrix U for all processors (PETSC_COMM_WORLD). I only want
> > > to copy only two rows (i,j) for each local processor. i,j is different
> > > for each processor and not related to rank.? I was trying to use a vector
> > > filter (like, 00000010000). However, if the vector is PETSC_COMM_WORLD,
> > > it will be changed by different processor. So, how to make it ?
> >? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> >? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> >? ? ? ? ? ? ? ? ? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >
> >? ? I do not understand what this means. To do the multiply you can and
> >should use a vector of PETSC_COMM_WORLD.
> >
> >? ? Also multiplying by a vector will not give you back "rows" of a matrix.
> >Do you truly want the entire row of nonzeros of the matrix or something
> >else. If you want the entire row or part of a row then you can use
> >MatGetSubMatrix().
> >
> >? ? Barry
> >
> > > Thank you
> > >
> > > My original code is
> > >
> > > Vec filter
> > > VecCreate(PETSC_COMM_WORLD,&filter);
> > > VecSetsizes(filter,PETSC_DECIDE,m);
> > > VecSetFromOptions(filter);
> > >
> > > Vecset(filter,0);
> > > VecSetValue(filter,i,1,INSERT_VALUES);
> > >
> > > ...
> > > MatMult(U, filter,ui);
> > >
> > > If I create filter with PETSC_COMM_SELF, it is impossible for U and
> > > filter to multiply.
> > >
> > >
> > >
> > >
> > >
> > > ?????????????????
> >
> >
> > ?????????????????
>
>
> ?????????????????
___________________________________________________________
?????????????????
http://card.mail.cn.yahoo.com/
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20091202/30912a47/attachment.htm>
