## Computational Resources

The memory needed to fit a model is approximately **24(***n*+2)^{2} bytes,
where *n* is the number of parameters estimated.
For models with more than two response levels, a test of the
parallel lines assumption requires an additional memory of approximately
**4***k*^{2}(*m*+1)^{2} + 24(*m*+2)^{2} bytes, where *k* is the number of
response levels and *m* is the number of slope parameters.
However, if this additional memory is not available, the procedure
skips the test and finishes the other computations. You may need
more memory if you use
the SELECTION= option for model building.

The data that consist of relevant variables (including the design
variables for model effects) and observations for fitting the model
are stored in the utility file. If sufficient memory is available,
such data will also be kept in memory;
otherwise, the
data are reread from the utility file for each evaluation of
the likelihood function and its derivatives, with the resulting
execution time of the procedure substantially increased.

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.