Am Montag, 20. April 2015, 14:57:58 schrieb Lisandro Dalcin:
> On 20 April 2015 at 14:35, Florian Lindner <mailingli...@xgm.de> wrote:
> > Hello,
> >
> > I use an index set for a row mapping but don't want to use one for the
> > column mapping.
> >
> > I try to create an idenitity index set to supply to
> > ISLocalToGlobalMappingCreateIS and MatSetLocalToGlobalMapping:
> >
> > IS is;
> > ISCreate(PETSC_COMM_WORLD, &is);
>
> At this point the index set does not have the type set.
>
> > ISSetIdentity(is);
> >
> > but I get an segmentation fault at the last line.
> >
>
> Bad error checking, you should get an error saying that the type is not yet
> set.
>
> > What is the best way to create an identity index set?
> >
>
> I would use ISCreateStride(), and perhaps next ISToGeneral() if you
> really want a ISGENERAL type.
All I want is an identity index set, that I can use with
ISLocalToGlobalMappingCreateIS and MatSetLocalToGlobalMapping.
Problem is when I know only the local size, not the global size of the matrix
ISCreateStride(PETSC_COMM_WORLD, nLocal, 0, 1, &is); followed by
ISAllGather(is, &isg); gives an IS like that:
0 0
1 1
2 2
3 3
4 0
5 1
6 2
7 3
so 0 to 3 are mapped twice, while the rest is not mapped. Just using the local
IS, without ISAllGather gives an Argument out of range at MatSetValuesLocal.
EDIT: Got it now using:
ISCreateStride(PETSC_COMM_WORLD, A.ownerRange().second -
A.ownerRange().first, A.ownerRange().first, 1, &is);
ISSetIdentity(is);
ISView(is, PETSC_VIEWER_STDOUT_WORLD);
ISAllGather(is, &isg);
if (rank==0)
ISView(isg, PETSC_VIEWER_STDOUT_SELF);
ISLocalToGlobalMapping mapping;
ISLocalToGlobalMappingCreateIS(isg, &mapping);
MatSetLocalToGlobalMapping(A.matrix, mapping, mapping);
based on the owner range.
