MatGetSubMatrix_MPIDense()

[Yujie]

The bug is strange. When I increase or reduce the processors, the bug will
appear with certain processors number :(.

On Tue, Jan 20, 2009 at 5:34 PM, Matthew Knepley <knepley at gmail.com> wrote:

> That fixes a bug since the the data is actually stored with leading
> dimension lda, rather
> than nlrows.
>
>  Matt
>
> On Tue, Jan 20, 2009 at 7:27 PM, Yujie <recrusader at gmail.com> wrote:
> > Dear Barry and Matthew:
> >
> > I always fingure out what's wrong with MatGetSubMatrix_MPIDense() in my
> > application. Because I use other pacakges based on PETSc, it is difficult
> to
> > change my PETSc2.3.3 to 3.0.0. I have to debug my codes to find
> something.
> >
> > Now, I have confirmed the question is in "*bv++ = av[irow[j] - rstart];"
> of
> >
> > (PETSC2.3.3)
> >
> > /* Now extract the data pointers and do the copy, column at a time */
> > 245: newmatd = (Mat_MPIDense*)newmat->data;
> > 246: bv = ((Mat_SeqDense *)newmatd->A->data)->v;
> > 247:
> > 248: for (i=0; i<ncols; i++) {
> > 249: av = v + nlrows*icol[i];
> > 250: for (j=0; j<nrows; j++) {
> > 251: *bv++ = av[irow[j] - rstart];
> > 252: }
> > 253: }
> >
> > The codes generate an error of segmentation violation.
> >
> > I have checkec PETsc3.0.0 version. the corresponding codes are:
> >
> > 220: /* Now extract the data pointers and do the copy, column at a time
> */
> > 221: newmatd = (Mat_MPIDense*)newmat->data;
> > 222: bv = ((Mat_SeqDense *)newmatd->A->data)->v;
> > 223:
> > 224: for (i=0; i<ncols; i++) {
> > 225: av = v + ((Mat_SeqDense *)newmatd->A->data)->lda*icol[i];
> > 226: for (j=0; j<nrows; j++) {
> > 227: *bv++ = av[irow[j] - rstart];
> > 228: }
> > 229: }
> >
> > why change "nlrows" to "((Mat_SeqDense *)newmatd->A->data)->lda"? After I
> > revise the codes in PETsc2.3.3, the error disappears. However, the
> results
> > from my codes become wrong. Could you give me some advice? thanks a lot.
> >
> > Regards,
> >
> > Yujie
> >
> >
>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which
> their experiments lead.
> -- Norbert Wiener
>
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