1) GIMPS has a new sub-project -- finding (probable) prime Mersenne cofactors.
This sub-project has two parts: 1) Running PRP tests, and 2) Finding
additional factors. To support this new sub-project there are three
new work preferences: PRP on Mersenne cofactors, PRP double-checking on
Mersenne cofactors, ECM on Mersenne cofactors.
2) Like LL tests, PRP tests now support shift counts to aid in running double-checks.
Shift counts are only supported for Mersenne numbers and Mersenne cofactors.
3) PRP tests now support a type of low overhead error checking that almost guarantees
correct results even on flaky hardware. We call this Gerbicz error-checking after
it was proposed by Robert Gerbicz at mersenneforum.org. This error-check only
works for base-2 numbers.
4) Because PRP tests are highly reliable, we now offer the option to do PRP tests
instead of Lucas-Lehmer primality tests. There are 3 new work preferences
similar to LL work preferences: first-time PRP tests, world record PRP tests,
PRP tests on 100 million digit numbers, and PRP double-checking.
If you are looking for a 100 million digit prime, PRP testing is recommended
rather than LL testing.
5) For non-base-2 PRP tests, there is a new option to run each iteration twice and
rollback if a mismatch occurs. Useful only on flaky hardware due to the obvious
high overhead.
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