On Tue, Apr 14, 2015 at 6:25 PM, Gideon Simpson <gideon.simp...@gmail.com> wrote:
> So other than the minor point of it zeroing out the data, is there any > conceivable reason to use Create/Destroy over Get/Restore? > Nope, and calling VecSet(v, 0.0) is really cheap. Matt > -gideon > > On Apr 14, 2015, at 7:16 PM, Matthew Knepley <knep...@gmail.com> wrote: > > On Tue, Apr 14, 2015 at 6:15 PM, Gideon Simpson <gideon.simp...@gmail.com> > wrote: > >> Other than zeroing things out, is there any substantive difference >> between DMCreateLocalVector and DMGetLocalVector? >> > > The Get version caches vectors, so you are not continually > creating/destroying > > Matt > > >> -gideon >> >> > On Apr 14, 2015, at 7:02 PM, Barry Smith <bsm...@mcs.anl.gov> wrote: >> > >> > >> > When PETSc vectors are created initially they always have 0 >> everywhere. So if you use DMCreateLocalVector() it will have zero in all >> those ghost places (as well as everywhere else). >> > >> > But if you use DMGetLocalVector() it returns vectors that maybe dirty >> so you need to fill in any locations you want to have a known value with >> that known value. Or call VecSet() to clear the entire vector. >> > >> > Barry >> > >> >> On Apr 14, 2015, at 5:52 PM, Gideon Simpson <gideon.simp...@gmail.com> >> wrote: >> >> >> >> If i use the DM_BOUNDARY_GHOSTED flag in the creation of a DMDA array, >> are the ghosted values automatically set to zero, or should they be >> manually set to zero if that’s the desired ghost value? >> >> >> >> -gideon >> >> >> > >> >> > > > -- > 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