Originally posted by MikeH
I'd suggest doing it for both.

Another option is to track supersecret, and raise the limit at (say) 100K or 200K thresholds when supersecret is about to hit the current given threshold. I think we have to agree that once candidates have PRPs with matching residues (i.e. double check) there is then zero value in continuing to sieve those ranges.
Mike et al,

Sure, doing both is ok for me too. I just proposed doing only Lower n because of two reasons:

- The marginal speed gain at Lower n would be much higher compared to Dual.
- I thought that some people might oppose a changeover at dual, and did not want to sacrifice a changeover at DC sieve.

But since we do not need factors for n<500K anymore, I guess there won't be many oppositions.

Tracking supersecret is a good idea too. But it really takes not much time prp testing for n<1m. So, what I'd propose is, tracking secret up to n=1m with 100K tresholds, and sticking with that lowerbound until supersecret reaches 1m. We can decide what to do next, looking at the sieve level we're at when supersecret hits 1m.

Any other suggestions?