data item the directory is written to the first random access record

and a "STOP 100" statement is executed. The random access space is also

saved instead of being deleted, as is the case with normal execution.

It then is possible to execute another job to examine the stored data

in order to determine the cause of the error.


5.3 Flow Diagram and Subroutine Descriptions

 The flow diagram for the executive program "GENIE" is shown in

Fig. 5-7. This program directs the derivation of the solution procedure

by following the paths shown in the flow diagram.

5.3.1 Decouple

 An attempt to decouple the set of equations by choice of index

decisions is made by a call to the subroutine "I1DCPL" which performs

the decoupling algorithm. If the algorithm succeeds, the equations are

rendered acyclic and the solution procedure is known. When this happens

GENIE has succeeded and control is returned to the calling routine.

5.3.2 Index Output Set Assign

 Should the set of equations not completely decouple, the equations

and variables which must be solved simultaneously are further analyzed.

The first step of this analysis is to assign index outputs. This is

done by a call to the subroutine "I2ISA" which in turn assigns the

outputs by calling the subroutine "HASSAL" (Cunningham, 1972, 1973).

This subroutine assigns outputs to the Index Display Matrices. The IDM

incidences are not merely 1's, but can have any integer value or weight.

HASSAL then assigns outputs in such a way that the sum of the weights

of the output elements is minimized (Gupta et al., 1974). This tech-

nique is useful if a term in an index equation is difficult to solve as