When Contexts change -- A New Context
Addition of a new context increments the value of lastctx
Assume that the last known value of lastctx is kept in a variable called oldctx.
- If oldctx not equal to lastctx on model entry, then new context has been allocated
- Copy the old context into the new context before doing anything else.
- Only need to do this within the DRR since we are keeping multiple copies of the ROBmap.