blocked index sets

[Dmitry Karpeev]

I would say that IS appears to be a *non-scalable* parallel object, since
the only parallel call
available for it seems to be ISAllGather (and variants).
It also seems to me that the real use for an IS is as input to the
ISLocalToGlobalMapping routines and it is
the mapping object that is truly global.

As a test for IS being global, can one imagine a circumstance when the same
IS
can be used with two different mappings which carry different comms?

I also want to point out that, in retrospect, Sieve is an evolution of the
IS/ISLocalToGlobalMapping
set of ideas.

Dmitry.

On Wed, Aug 27, 2008 at 1:16 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Aug 27, 2008 at 1:08 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > On Aug 27, 2008, at 12:13 PM, Matthew Knepley wrote:
> >
> >> On Wed, Aug 27, 2008 at 12:06 PM, Lisandro Dalcin <dalcinl at gmail.com>
> >> wrote:
> >>>
> >>> So, Do all us agree my proposed fix should be pushed? I'll wait for
> >>> Matt comments/complaints...
> >>
> >> I complain that IS is a fake parallel object.
> >
> >  In what way is IS a fake parallel object? Maybe we can resolve
> > your concern about it being a fake parallel object.
>
> I said fake because it has a single collective operation (or even one
> with communication).
> We even use IS in situations where GetSize() makes no sense, or at least
> are not
> careful about the comm used. Also, none of the other functions work
> over the comm.
> For instance, the ISIsPermutation() or ISSorted() do not look at the
> indices collectively.
>
>  Matt
>
> >   Barry
> >
> >
> >> However, if
> >> GetSize/GetLocalSize already
> >> do this, then yes we should change the ISBlock version as well.
> >>
> >>  Matt
> >>
> >>> On Wed, Aug 27, 2008 at 1:13 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> >>>>
> >>>> On Aug 27, 2008, at 10:23 AM, Matthew Knepley wrote:
> >>>>
> >>>>> There is no concept of global for IS. They are purely serial. AO is
> the
> >>>>> only
> >>>>> global construct with indices.
> >>>>
> >>>>  This is kind of true, and maybe used to be completely true. But IS
> does
> >>>> have a communicator and that communicator can be MPI_COMM_WORLD or
> >>>> any parallel communicator.  In other words the IS is evolving to be an
> >>>> object
> >>>> that can be parallel in the same sense as vecs or mats
> >>>>
> >>>>  There are already ISGetSize() and ISGetLocalSize() so it sure makes
> >>>> sense
> >>>> to have the same paradgm for the ISGetBlockSize().
> >>>>
> >>>>
> >>>>  Barry
> >>>>
> >>>> Originally IS had no parallel concept, then we added the
> >>>> ISGetSize/LocalSize
> >>>> but forgot to do it for the ISBlock...
> >>>>
> >>>>
> >>>>>
> >>>>>
> >>>>> Matt
> >>>>>
> >>>>> On Wed, Aug 27, 2008 at 10:09 AM, Lisandro Dalcin <dalcinl at gmail.com
> >
> >>>>> wrote:
> >>>>>>
> >>>>>> I believe we have to review the interface of ISBlock. Currently,
> >>>>>> ISBlockGetSize() return the number of LOCAL block indices. This is
> not
> >>>>>> consistent with other naming conventions for getting local and
> glocal
> >>>>>> sizes. I propose to change this to the following
> >>>>>>
> >>>>>> 1) change: ISBlockGetSize() returns the number global blocks
> >>>>>> 2) addition:  ISBlockGetLocalSize() return the number of local
> blocks
> >>>>>>
> >>>>>> Comments?
> >>>>>>
> >>>>>>
> >>>>>> --
> >>>>>> Lisandro Dalcín
> >>>>>> ---------------
> >>>>>> Centro Internacional de Métodos Computacionales en Ingeniería
> (CIMEC)
> >>>>>> Instituto de Desarrollo Tecnológico para la Industria Química
> (INTEC)
> >>>>>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> >>>>>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> >>>>>> Tel/Fax: +54-(0)342-451.1594
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>> 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
> >>>>>
> >>>>
> >>>>
> >>>
> >>>
> >>>
> >>> --
> >>> Lisandro Dalcín
> >>> ---------------
> >>> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> >>> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> >>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> >>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> >>> Tel/Fax: +54-(0)342-451.1594
> >>>
> >>>
> >>
> >>
> >>
> >> --
> >> 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
>
>
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