Experience with the implementation of related algorithms indicated that the
memory required for modeling large systems would be prohibitive. We
therefore looked for ways to conserve and reduce memory usage. There are
several tactics that we used in this implementation:
- Store data only at the active sites.
This is accomplished in the C implementation by representing the medium as a
three dimensional array of pointers. At each active site the pointer
references a data structure with the necessary velocity and mass data. At the
inactive sites the pointer is NULL; no additional storage is required at
the inactive sites. For a low porosity medium the memory
savings are very large.
- Assume that = 1.
This assumption simplifies evaluation of equations 1-5 such
at each active site we need only store the density of
each fluid component, and a single velocity vector.
Without this assumption, we must store all 19 values
associated with the velocity distribution, ni, at each site.
- Only one copy of the data volume is stored.
Rather than keeping an entire second data volume in which
to accumulate the newly calculated data, we exploit the
fact that the algorithm only uses nearest neighbors
at each site.
Thus we only
need an additional buffer of three planes of data at any one
Assuming that floating point numbers and C pointers each take four bytes,
these memory optimizations yield savings of over 94 % of memory usage in
the one component case for systems of useful sizes. The memory savings are
even greater when more fluid components are used or when larger floating
point representations are used.