"crossed-out" rows and columns. The SIMl as it was before the elim-

ination of unneeded rows and columns is stored and its name put on the

stack for possible access later. If a proposed tear variable is ever

found to be the complement of a torn two-way edge variable, the SIM on

which this decision was made is restored and the tear choices for that

two-way edge are reversed by J1FIX. If an SIM must be restored from

mass memory RDDISK is called to do this.

 Whenever J1FIX is called, the algorithm backtracks, and thus no

longer needs some of the stored SIM's. These are marked as not needed,

and CLRMEM is called to clear them from MEMORY.

 The algorithm terminates when the SIM being operated on becomes

null. If SEARCH ever fails to find an SIM, a STOP 105 statement is

executed.

B.1.2 IlDCPL

STONDX (3.1), STOSIM (3.2), RELNAM (5.9), RSTNDX (5.10), RSTSIM (5.11),

SUBSIM (5.12), CALCDC (6.2), CLRMEM (6.3), HASSAL (6.5), RDDISK (6.16),

SEARCH (6.17), SPEDUP (6.20), WRTDSK (6.22)

 The subprogram IlDCPL performs the decoupling algorithm. It

first stores the SIM and INDEX data areas in MEMORY using the sub-

programs STOSIM and STONDX. The execution of the decoupling algorithm

itself then begins.

 The SIM is reduced to the unassigned functions and variables

by SUBSIM. The subprograms HASSAL and SPEDUP are called to determine

whether the SIM fully precedence orders. If it does the original SIM

and INDEX data structures are restored using SEARCH (and WRTDSK and

RDDISK if the data areon mass memory), RSTSIM and RSTNDX.