[petsc-dev] [petsc-maint] Feature: allow unsorted row IS in MatGetSubMatrix_SeqAIJ()

[Tobin Isaac]

On Mon, Jan 19, 2015 at 02:06:16PM -0600, Barry Smith wrote:
> 
> > On Jan 19, 2015, at 1:36 PM, Tobin Isaac <tisaac at ices.utexas.edu> wrote:
> > 
> > If being sorted is a requirement of the interface, I think the ISSorted tests belong in the interface and not in the _SeqAIJ implementation; if it's not a requirement, then only the implementations that don't support unordered IS's should raise an ERR_SUP, right?
> 
>    Yes. But it appears with regard to sorting we've been rather scattershot on following your logic :-).

If I enforce the latter logic (raising errors) for the other
implementations and update the doc to reflect that, would that work?

> 
>    
> > 
> > On January 19, 2015 12:57:45 PM CST, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >> 
> >>  Should actually send these things to pets-dev
> >> 
> >>  The docs for MatGetSubMatrix() have the line
> >> 
> >> "The rows in isrow will be sorted into the same order as the original
> >> matrix on each process."
> >> 
> >>   The docs for MatGetSubMatrices() say 
> >> 
> >>  "Currently both row and column indices must be sorted to guarantee
> >>  correctness with all matrix types."
> >> 
> >> PetscErrorCode MatGetSubMatrices_MPIAIJ(Mat C,PetscInt ismax,const IS
> >> isrow[],const IS iscol[],MatReuse scall,Mat *submat[])
> >> {
> >> PetscErrorCode ierr;
> >> PetscInt       nmax,nstages_local,nstages,i,pos,max_no,nrow,ncol;
> >> PetscBool     
> >> rowflag,colflag,wantallmatrix=PETSC_FALSE,twantallmatrix,*allcolumns;
> >> 
> >> PetscFunctionBegin;
> >> /* Currently, unsorted column indices will result in inverted column
> >> indices in the resulting submatrices. */
> >> /* It would make sense to error out in
> >> MatGetSubMatrices_MPIAIJ_Local(), the most impl-specific level.
> >> However, there are more careful users of
> >> MatGetSubMatrices_MPIAIJ_Local() -- MatPermute_MPIAIJ() -- that
> >> take care to order the result correctly by assembling it with
> >> MatSetValues() (after preallocating).
> >>  */
> >> for (i = 0; i < ismax; ++i) {
> >>   PetscBool sorted;
> >>   ierr = ISSorted(iscol[i], &sorted);CHKERRQ(ierr);
> >> if (!sorted) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_SUP, "Column index set
> >> %D not sorted", i);
> >> }
> >> 
> >> In other words the sorted business seems a little wacky at the moment. 
> >> I'm not sure what to conclude.
> >> 
> >> 
> >>  Barry
> >> 
> >>> On Jan 19, 2015, at 11:36 AM, Tobin Isaac <tisaac at ices.utexas.edu>
> >> wrote:
> >>> 
> >>> 
> >>> There doesn't seem to be any reason for MatGetSubMatrix_SeqAIJ() to
> >>> require the row IS to be sorted, and this requirement differs from
> >>> other implementations, e.g. _MPIAIJ.  I have a feature branch that
> >>> removes the requirement.  Can I merge it into next for testing?
> >>> 
> >>> Thanks,
> >>> Toby
> > 
> 
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