Re: [pooma-dev] Memory overhead

[Jeffrey Oldham]

On Tue, May 07, 2002 at 06:59:00PM +0200, Nils H. Busch wrote:
> Hello,
> 
> can someone give me a rough estimation of what will be the memory
> overhead for using Pooma::Arrays and Pooma::Fields.
> 
> For using small arrays/fields, my experiments showed that there seems to
> be a constant base amount of about 6MB (using Pooma v 2.3 on an Origin
> 2000 with SGI CC v 7.3).
> For larger arrays/fields the ratio of memory needed theoretically for a
> data set to the memory actually occupied showed roughly a 60% overhead
> for the latter.
> 
> Is this reasonable ? Which parts of pooma require the additional memory
> ? First, I thought, the 60% increase would only happen when using Fields
> and the underlying position arrays needed the extra memory,
> but using arrays showed the same increase.
> 
> Also, the old tutorial states that all mesh classes have guard layers
> the size of N/2, N being the number of vertices along an axis. For large
> high-dimensional meshes, I think, this could be quite a large memory
> overhead, if actually memory is allocated for the guard layers. Is
> really memory allocated and if so, can this fixed guard layer size be
> adjusted to what is really required prior to memory allocation ?

The new Field interface, available from the POOMA CVS tree, permits
specifying the mesh so explicit control of the guard layers is
permitted.

> Thanks for any comments.

Thanks,
Jeffrey D. Oldham
address@hidden