PETSc

[Matthew Knepley]

On 1/27/07, Aron Ahmadia <aja2111 at columbia.edu> wrote:
>
> Sounds like a documentation bug to me, are you referring to this?
>
> http://www-unix.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/DA/DARestoreGlobalVector.html#DARestoreGlobalVector
>
> Perhaps I'm misunderstanding how Get/Restore are being used.  I'll let
> one of the developers chime in on this when they've got a moment.


This is a cut&paste error from GetLocalVector().

  Matt

~A
>
> On 1/27/07, Brian Grierson <bag2107 at columbia.edu> wrote:
> > Another quick question.  PETSc online help says
> DAGetGlobal/DARestoreGlobal
> > is a Seq vector operation, while
> > DACreateGlobal/VecDesroy is parallel.
> >
> > I don't understand how you could create a global vector in a Seq manner
> on a
> > DA???
> >
> >
> >
> > Brian A. Grierson
> >
> >
> >
> >
> > Department of Applied Physics
> >
> > Columbia University
> >
> > Mobile: 646.259.1038
> >
> > Work:    212-854-4839
> >
> > bag2107 at columbia.edu
> >
> > bgrierson21 at gmail.com
> >
> >
> http://www.columbia.edu/~bag2107/http://www.apam.columbia.edu/ctx/ctx.html
> >
> >
> > On Jan 27, 2007, at 6:41 PM, Aron Ahmadia wrote:
> >
> > Hi Brian,
> >
> > I took a quick peek at the source for DAGetGlobalVector in the current
> > release:
> >
> > "
> >  for (i=0; i<DA_MAX_WORK_VECTORS; i++) {
> >    if (da->globalin[i]) {
> >      *g             = da->globalin[i];
> >      da->globalin[i] = PETSC_NULL;
> >      goto alldone;
> >    }
> >  }
> >  ierr = DACreateGlobalVector(da,g);CHKERRQ(ierr);
> >
> >  alldone:
> >  for (i=0; i<DA_MAX_WORK_VECTORS; i++) {
> >    if (!da->globalout[i]) {
> >      da->globalout[i] = *g;
> >      break;
> >    }
> > "
> >
> > The two appear to be very similar, with this exception.  Get/Restore
> > work with one copy of the DA's global vector, but will make a copy if
> > one has already been checked out or none exist.
> >
> > DACreateGlobalVector will always make a copy of the global vector,
> > regardless of the circumstances.   I think you're better off using Get
> > and Restore (less data copying) unless you'd like to work with
> > multiple copies for some reason.
> >
> > ~A
> >
> > On 1/27/07, Brian Grierson <bag2107 at columbia.edu> wrote:
> >
> > Could you please tell me the difference between
> >
> > DACreateGlobalVector / VecDestroy
> > and
> > DAGetGlobalVector / DARestoreGlobalVector
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Brian A. Grierson
> >
> >
> >
> >
> > Department of Applied Physics
> >
> > Columbia University
> >
> > Mobile: 646.259.1038
> >
> > Work:    212-854-4839
> >
> > bag2107 at columbia.edu
> >
> > bgrierson21 at gmail.com
> >
> >
> http://www.columbia.edu/~bag2107/http://www.apam.columbia.edu/ctx/ctx.html
> >
> >
> >
> >
>
>


-- 
One trouble is that despite this system, anyone who reads journals widely
and critically is forced to realize that there are scarcely any bars to
eventual
publication. There seems to be no study too fragmented, no hypothesis too
trivial, no literature citation too biased or too egotistical, no design too
warped, no methodology too bungled, no presentation of results too
inaccurate, too obscure, and too contradictory, no analysis too
self-serving,
no argument too circular, no conclusions too trifling or too unjustified,
and
no grammar and syntax too offensive for a paper to end up in print. --
Drummond Rennie
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