[Users] GF information question

[Frank Loeffler]

On Thu, Nov 19, 2015 at 11:05:24PM -0600, Frank Loeffler wrote:
> The best way would probably be to count them locally on each process,
> write the result in a distributed grid array, and do the sum there by
> syncing the array and counting locally (not sure if a reduction on such
> an array would work, it might).

One complication here would be that, with AMR at least, you would need
to take care of masking non-evolved points (ghost, boundary, coarse grid
points inside fine grids, ...).

> Another, but more expensive way (in terms of memory size and memory
> accesses) would be to create another grid function, populate it with
> either 1 or 0 depending on the non-zero-property of the GF you are
> interested in, and calling the existing sum-reduction on it.

Here you wouldn't need to care about masking, as the Carpet reduction
would do that for you.

Frank

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