Suppose that your computer is equipped with a main memory and a scratchpad memory. Sizes and the required energy per access are shown in Table 7.2 (right). Characteristics of accesses to variables are as indicated in Table 7.2 (left).

Which of those variables should be allocated to the scratchpad memory, provided that we use a static, non-overlaying allocation of variables? Use the integer linear problem (ILP) model to select the variables. Your result should include the ILP model as well as the results. You may use the lp_solve program [17] to solve your ILP problem.

Table 7.2 SPM mapping: left, accesses to variables; right, memory characteristics Number of Variable Size [bytes] accesses a 1024 16 b 2048 1024 C 512 2048 d 256 512 Energy Memory Scratchpad Size [bytes] per access 4096 (4k) 1.3 nJ Main memory 262,144 (256 k) 31 nJ