pub fn ecm(n: &BigInt, budget: usize, seed: u64) -> Option<BigInt>Expand description
ECM stage 3 — the escalating driver. Stages 1 and 2 are the algorithm; this is the orchestration that
makes ECM a complete tool (à la GMP-ECM): run the two-stage method at a schedule of increasing bounds
(b1, b2 = 100·b1) with growing curve counts, so a factor of any size is found at the cheapest level
that reaches it — small factors fall almost immediately, larger ones as the bounds climb, without ever
paying the big-bound cost up front. budget caps the curves per level. None if the whole schedule
finishes without a factor.