Memory overhead

[Nils H. Busch]

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 ?

Thanks for any comments.

--
    Nils H. Busch
    Max-Planck-Institute of Cognitive Neuroscience
    phone:  ++49 (341) 9940-335 fax:  ++49 (341) 9940-204
    e-mail: nilsb at cns.mpg.de