[Users] nature of Cactus

[Erik Schnetter]

On Nov 11, 2006, at 07:54:29, David Rideout wrote:

> The particular parallel scenario you describe sounds like what we
> refer to as a "multi-model" simulation.  You have different physics in
> different regions, and may want to run those different regions on
> different machines, while still allowing the various models to
> communicate.  This is something that comes up in climate modeling as
> well, so I know that people have been thinking about this in the
> context of Cactus.
> Something like this has been done for binary black hole simulations
> with Cactus using globus for the MPI layer.
> Perhaps others on the list will know more about the current status.
> Generic support for these sorts of simulations is planned for Cactus
> 5.  (Or perhaps 4.1, see
> http://www.cactuscode.org/Development/current.html.)

There is some prototype multi-model support in the Carpet driver.   
For example, you may want to solve the full Einstein equations in the  
nonlinear regime, and solve a linearised version in the far-field.   
In the prototype, one is essentially running independent simulations  
(with different active thorns, different parameter setting etc.),  
which communicate through boundary conditions.  The communication  
happens via what Cactus calls "hyper-slabbing", which is exchanging  
of data in rectangular or cuboidal regions.

However, we don't use that in production mode yet, so that it is  
likely still inconvenient to use, or still has errors.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

My email is as private as my paper mail.  I therefore support encrypting
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