Sometimes one has to make compromises between speed of execution and memory, other times one may not have to be. While working towards a fairly (at least in my mind) complete solution to map Nanopore Sequencing files, I ran against the need to create and access fairly large hash of arrays (think of 1M - 100Mof keys), with each array itself consisting of a a fixed number of elements.

The hash of arrays is a fairly straightforward and fast data structure to create in Perl, the memory overhead can be substantial as the number of keys and values scale upwards.…