Re: [pooma-dev] Sparse Engine

[Richard Guenther]

On Fri, 26 Sep 2003, Sergei Mingaleev wrote:

> Hello, Jean:
>
> >> John and I are starting to write a sparse engine -- for sparse storage of
> >> our material-dependent fields.
> >> ....
> >> only demonstrates how to build the engine, not an array or a field.  Could
> >> someone please show us how to move forward with this example to building a
> >> complete array and field version?
>
> I has written some time ago a simple version of the SparseEngine -
> see it attached.  At the momemnt the Engine works only with 2D
> and 4D arrays, and it cannot be parallelized.

I think this notion of a sparse engine is different from Jeans. In fact
the whole point of sparsity in Jeans case is probably the multi-material
stuff and resulting optimizations (which I dont get completely at the
moment).

Just the sparsity you invented looks like it could be done better by
having a (possibly shared) bitmap of valid locations and a evaluator
taking that into account. Memory usage would be reduced by not accessing
the unused parts and such only wasting virtual memory. Of course the
bitmap (if not changing) could be compressed f.i. with a run-length
encoding. This should be an efficient way to have arbitrary
shaped boundaries at least in the serial case. For the parallel case you'd
probably need to do some clever load balancing tricks to not get hurt by
mostly "empty" bricks.

Richard.