On Wed, Jan 4, 2012 at 10:40, Matthew Knepley <knepley at gmail.com> wrote:
> I have just noticed that MatGetRowMinAbs (but not the Max variant) in >> some cases returns a very small negative number like -1.62505e-17 >> (displayed as %g). Is this an epsilon effect or an indication of a >> problem? >> > > Its not possible that was actually the minimum element? > It is supposed to be returning the absolute value anyway, so no. Also, due to this patch of yours http://petsc.cs.iit.edu/petsc/petsc-dev/rev/e433a0 it should never return a value smaller than 1e-12 that isn't identically zero. I don't understand why this shift is being done, but I think that if you want a shift like this, it should at least be relative to the norm of the vector or something. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120104/e6e40863/attachment.htm>
