Het distributed-computingproject Gimps, wat staat voor Great Internet Mersenne Prime Search, zoekt naar Mersenne-priemgetallen. Dat zijn priemgetallen die precies één kleiner zijn dan een macht van twee, ofwel 2n - 1. De eerste vier n-getallen om de eerste vier Mersenne-priemgetallen mee te vormen zijn 2, 3, 5 en 7, waar respectievelijk 3, 7, 31 en 127 uitkomt. Het benodigde programma heet Prime95 en wordt onder een eigen licentie uitgebracht. Versie 29.8 build 3 is onlangs verschenen voor FreeBSD, Linux (32, 64bit), macOS en Windows (32, 64bit), ook kun je natuurlijk de broncode binnen hengelen. De lijst met verbeteringen ziet er als volgt uit:
New features in Version 29.8 of prime95.exeNew features in Version 29.4 of prime95.exe
- Support added for AVX-512 FFTs.
- FMA3 FFTs now have slightly higher FFT crossover points. Soft crossovers are no longer used by default. See undoc.txt.
- Torture test dialog box options now based on cache sizes. Options for performing a weaker torture test are available. Torture tests that use all RAM are now more stressful. In-place vs. not in-place memory accesses now displayed on screen. On machines with more than 5GB of memory, blend defaults to all but 3GB of RAM.
- Add & subtract operations for AVX-512 FFTs are now multithreaded. This should improve performance for P-1 and ECM when using multiple threads.
- Benchmark results are now written to results.bench.txt.
- JSON results are now available for all work performed. JSON results are written to results.json.txt.
- PRP tests with Gerbicz error checking are more immune to hardware errors.
New features in Version 29.3 of prime95.exe
- 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.
- 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.
- 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.
- Because PRP tests are highly reliable, we now offer the option to do PRP tests instead of Lucas-Lehmer primality tests. There are 4 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.
- 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.
- Minor performance tweaks were made to stage 1 of P-1. Save files are incompatible in stage 1. Wait for your P-1 test to reach stage 2 before upgrading.
- A new error check for LL testing has been implemented. This error check, called a Jacobi error check, has a 50% chance of detecting hardware error(s) since the last time a Jacobi error check was performed. This error check takes roughly 30 seconds and is scheduled to run twice a day. The program now saves two additional intermediate files that have passed the Jacobi error check. This test requires use of the GMP (GNU multi-precision) library.
- The GCD step in P-1 and ECM factoring is faster.
