Migration
n Array objects can migrate from one PE to another
n To migrate, must implement pack/unpack or pup method
n Need this because migration creates a new object on the
destination processor while destroying the original
n pup combines 3 functions into one
Data structure traversal : compute message size, in bytes
Pack : write object into message
Unpack : read object out of message
n Basic Contract : here are my fields (types, sizes and a
pointer)