Software update: Prime95 29.8

The distributed computing project Gimps, which stands for Great Internet Mersenne Prime Search, searches for Mersenne primes. Those are primes that are exactly one less than a power of two, or 2n – 1. The first four n numbers to form the first four Mersenne primes are 2, 3, 5 and 7, where 3, 7, 31 and 127 comes out. The required program is called Prime95 and is listed under a own license released. Version 29.8 build 3 is recent appeared for FreeBSD, Linux (32, 64bit), macOS and Windows (32, 64bit), of course you can also fish the source code. The list of improvements looks like this:

New features in Version 29.8 or 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 29.4 or 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 or P-1. Save files are incompatible in stage 1. Wait for your P-1 test to reach stage 2 before upgrading.

New features in Version 29.3 or prime95.exe

• 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.