The first level of computer use in science and engineering is modeling.
Beginning from physical principles and design ideas,
the computer mimics nature.
After this, the worker looks at the result and thinks a while,
then alters the modeling program and tries again.
The next, deeper level of computer use is that the computer itself
examines the results of modeling and reruns the modeling job.
This deeper level
is variously called
We inspect the conjugate-direction method of fitting
and write a subroutine for it that will be used in most of
the examples in this monograph.