Function polylog_memory 

pub fn polylog_memory(n: usize, c: f64) -> usize

Poly-logarithmic memory p_n = ceil(c · log n), clamped to [2, n/4]. This is the window size covered by the uniform law-of-the-iterated-logarithm bounds for sample autocovariances (Hannan & Deistler 1988, Thm 5.3.2; Bauer 2001, Lemma 1), hence a candidate default pending theory work. c = 2 gives 9 at n=100, 14 at n=1000, 19 at n=10⁴.