With Evolving Dimensions

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: With Evolving Dimensions
• From: cje@xxxxxxxxxxxxxx (C James Elliott)
• Date: Fri, 27 Mar 1992 15:39:00 MST

In regards to the recent spate of concerns of data format, it
might be helpful to include some views from generators of data
whose structure evolves in time. I will sketch their structure.
The first is a particle-in-cell code that describes accelerator
configurations.  When the particles are first populating the region
near the cathode of the injector, they are stored in arrays of
small size.  During the parturation, the arrays grow in size.
Later when some of the stragglers strike the wall and desist, the
array size diminishes. A second such example is the finite element
structure of the code TOSCA that is used for calculations of magnetic
fields.  That structure is of the extrusion variety.  The (x,y)
grid characteristics evolve with extrusion parameter z. A third 
example is in hydro codes where because of scale size changes,
remeshing with more grid points is required.

Mike Jones solved the variable dimension problem by what I believe
is an upwardly compatable modification.  He simply increased the
allowable number of arrays.  He assigned new variable names to
each time step, e.g. (x1,y1), (x2,y2),...(x777,y777). Note, however,
netCDF is currently used only in the first problem. Earlier graphics 
packages were established for hydro and the proliferation of results 
is not always desirable.  In the TOSCA case data archival is a major
focus, but global
 data exchange is not a driving concern.

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