As George has already pointed out, among others, the list of k values tried in gpu trial factoring is not reproducible from run to run of a given exponent/bit level combination, because the factor candidate sieving is not deterministic, letting some composite factors through to be tried against the mersenne number. It's done that way because it's faster than a perfect factor candidate sieving to primes only.
That means the list of k values will vary, so the n.10^cth k value will vary, so the crc will vary, for the same inputs. To fix that issue, would require completely sieving each factor candidate, not just every 10^c.
I think Gerbicz' approach is more easily made immune to this leakysieve issue.
And since it is a singleword binary mod of something that's already been moded down to factor size, that part should be very quick. Only the factor candidates for the Gerbicz check values list need be further screened for primeness.
Last fiddled with by kriesel on 20200502 at 18:34
