Assignment of program units to minimize the number of calls between memory blocks

When assigning program units (functions) to memory blocks in many embedded microprocessor devices, the actual size of the program units can depend on the assignment. When blocks of memory represent different physical devices/locations, calling program units in the same block requires the minimum amount of memory. When calling units in a different memory block, a longer absolute address must be used. When memory availability is short, as in products like pagers and cellular telephones, careful assignment of program units to memory blocks can free up significant amounts of memory. A set of non-linear (quadratic) expressions can be formulated to describe the memory limitation and program unit constraints. To minimize the memory usage, the number of function calls across memory blocks should be minimized. Also, memory blocks that are nearly full present a problem. If the units in a block grow to a total size larger than the block size, units must be reassigned to different blocks. This typically results in a ripple effect causing an undesirable widespread reassignment of units. Leveling the usage in each block is therefore desired. This paper presents the math programming formulation for the program unit assignment problem and several solution approaches