On Thu, Jan 5, 2012 at 4:07 AM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:
> Is it also possible that MaxAbs would be computed wrongly? I get a > different value when I compute it myself. Yes, that is possible. Here is the code: http://petsc.cs.iit.edu/petsc/petsc-dev/annotate/d1799f05bf01/src/mat/impls/aij/seq/aij.c#l2628 Matt > > Dominik > > On Thu, Jan 5, 2012 at 1:02 AM, Barry Smith <bsmith at mcs.anl.gov> wrote: > > > > On Jan 4, 2012, at 5:42 PM, Matthew Knepley wrote: > > > >> On Wed, Jan 4, 2012 at 5:29 PM, Dominik Szczerba <dominik at itis.ethz.ch> > wrote: > >> Do you think this issue can potentially explain a behavior I observe: > >> > >> In my big block shell matrix there are two blocks submatrices: (say) B > >> and B transposed. MaxAbs is exact same for both submatrices, MinAbs is > >> zero for B (as expected), but small negative for the other > >> (unexpected). > >> > >> Now question: do I have a bug (that I do not immediately see) or this > >> can be hopefully only a trick in MinAbs? > >> > >> It was a bug in MinAbs. I am pushing the fix. > > > > To 3.2 I hope. Please send the patch link for 3.2 as Satish did just > a little while ago for another bug. > > > > Barry > > > >> > >> Matt > >> > >> Thanks a lot. > >> > >> On Wed, Jan 4, 2012 at 6:05 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > >> > On Wed, Jan 4, 2012 at 11:02, Matthew Knepley <knepley at gmail.com> > wrote: > >> >> > >> >> Okay, here is what is wrong with the logic: > >> >> > >> >> 1) Its not a shift, it ignores values < 1.0e-12 > >> > > >> > > >> > you wrote that in the commit message > >> > > >> >> > >> >> > >> >> 2) The problem is on line 2.17 of the diff where it takes the first > value > >> >> as minimum, but does not take the absolute value > >> > > >> > > >> > good catch > >> > >> > >> > >> -- > >> 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 > > > -- 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120105/a930d534/attachment.htm>
