Constant MAX_POPULATION 

pub const MAX_POPULATION: usize = _; // 4_096usize

The largest population a run takes, 2¹². The sort of parents and children together keeps, for each design, the list of designs it dominates: up to about (2N)²/2 indices, some 270 MB on a 64-bit machine at this size (more while the lists grow), and four times as much for each doubling.