[Users] PUGH Questions

[Frank Loeffler]

Hi,

On Fri, May 09, 2008 at 02:04:55AM +0200, Andreas Schäfer wrote:
> * In a cluster with heterogeneous machines, can PUGH perform automatic
>   static load balancing to give faster machines more grid points?

No. You could distribute the data by hand probably, but AFAIK PUGH
cannot do that automatically. PUGH does not know about the machine
specifics like available memory.

> * Can PUGH perform dynamic load balancing?

No.

> * When I use numbers of nodes that are not powers of 2, the domain
>   decomposition sometimes degrades. For instance for 31 nodes a cube
>   would be decomposed into 31 thin slices, leading to a rather bad
>   surface to volume ratio. Is there any way to avoid such situations?
>   (using only powers of two as numbers of nodes is not an option ;-) )

PUGH will (by default) try to devide the domain evenly to all
processors with the restriction that you cannot have a processor domain
edge like this:
      domain 1
 ----------+----------
  domain 2 | domain 3
           |
Because 31 is a prime number, PUGH has no other option as to devide it
like you described. If you choose 30, it could devide e.g. into 2*3*5.

> * Are alternatives to PUGH available that perform better in regards to
>   the questions above?

I do not know one from the top of my head, but that does not mean that
there couldn't exist one. However, you might want to have a look into
Carpet (www.carpetcode.org), even if you do not intend to use mesh
refinement. I am not sure if Carpet could e.g. handle the last question
better. Erik Schnetter would be the right person to ask.

Frank