3 o Records of odd lengths.
7 o Use radix-sort for internal sorting.
8 o Parallelization of internal sorting.
9 o Clean up data types and make sure they cannot overflow. (size_t vs. u64 vs. sh_off_t vs. uns)
10 o Buffer sizing in internal sorters.
11 o Switching between direct and normal I/O.
12 o When merging, choose the output file with less runs instead of always switching?
13 o Deal with too rough range estimates in radix splitting.