treated merely as equations with no indices or as single index

equations, all of whose indices are restricted to a single value. The

ability to analyze non-indexed as well as indexed equations makes it

possible to analyze problems with equations of both types.

 The computer programs were written in such a way that the packages

of subroutines representing the various algorithms are "stand-alone"

programs. This means that a program package can be used independently

of the GENIE or GENDER system. This allows the user, for example, to

find the miminum weighted tear set for a flowsheet or set of equations

without having to generate an entire solution procedure.

 As was mentioned in Chapter 4, the set of tear variables chosen

has an effect on the convergence of a solution procedure. The criterion

adopted by GENIE for the selection of tear variables is to minimize the

number of tear variables. A better criterion would be to choose the

tear variable set which makes convergence most likely. Further research

would be required to develop criteria for selecting tear variables to do

that.

 Computer aids to design engineers, such as the GC ..-. or GENIE

systems, could be even more valuable if they were implemented inter-

actively, i.e., if the user could interact with the computer program

while it executes. Rather than terminating execution when more data or

a decision on the part of the user is required, tne program could "ask"

the user for the required information, and resume execution when it is

supplied. This would eliminate the need for running a program several

times to solve a single problem. Because of the size and complexity of

computer programs such as GENIE, this modification is possible only on

computers with sophisticated interactive time sharing systems.