[vtkusers] paralleliso isnt.

[Berk Geveci]

> When I was working on this last year with Scott Klasky at PPPL, it did
> scale very poorly and I believe that this is due in part to
> marshalling/unmarshalling the data.  I assume that the
> marshalling/unmarshalling has not changed in the past year.
> 

This is quite possible. I didn't run into it in my tests but I only
ran on up to 8 processors.

> I think Jim Ahrens pointed out to me at one time that the
> default marshalling/unmarshalling is in ASCII, but there is
> a method that can be used to force the vtkMPICommunicator to
> use binary.  Otherwise you get throttled by the cost of
> marshalling/unmarshalling the data (an incredibly slow
> process even on gigahertz CPU's).

The marshalling/unmarshalling is not done in ASCII (as far as I can
see, it's not even possible to force it to be ASCII). It has been this
way for at least a year (I really don't know when that was changed,
it must have been before I joined Kitware last year).

-- 
Berk Geveci, Ph.D.
Kitware, Inc.
VTK-Based Visualization Solutions
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