FN-1x Small Primes search starts 2021-01-21

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#1 FN-1x Small Primes search starts 2021-01-21

Post by Alez »

To continue efforts to create complete list of small GFN primes up to b=2G, a "Search for Small Primes" project will be started January 21, 2021, 09:00 UTC on "Private GFN server".

Note this is not a PrimeGrid project. It's running on a separate server, server address is http://boincvm.proxyma.ru:30080/test4vm/ (also note the non-standard port). If you're a new user here, you must create your account on the site first, using invitation code PrimeGrid. Automatic registration from Boinc client most probably will not work.

Project description

The goal is to create full list of GFN primes as far as software limit and computation resources allows. Historically, each sequence is tested, depending on it's complexity, either up to b=400M (old software limit) either up to b=2G. Current testing status is:

GFN-1 - GFN-11 - tested manually up to b=2G by a group of PrimeGrid users;
GFN-12 - wasn't tested to significant depth;
GFN-13, GFN-14 - tested on Private GFN server up to b=400M;
GFN-15 and above - currently tested on PrimeGrid.

In the first phase, we will test GFN-12 up to b=2G. There are plans to run second phase, extending GFN-13 search up to b=2G, but it'll require additional sieving, so it'll be a delay between first and second phase.

Primes found during this search will be relatively small and cannot be reported to any "top" list. We will find thousand of them. Although they'll be collected mostly for statistical purposes, these primes can be used as a starting points searching for "chains" or "twin" primes, which may lead to another interesting and reportable discoveries.

Technical details

The project is GPU only.

We'll use new generation of Yves Gallot' program, "Genefer 2.0". Designed exclusively to test small numbers (when each test takes just a few seconds), it can test many candidates at once, fully utilizing your GPU and requiring almost no CPU time. It also implements Gerbicz error checking to detect hardware errors in GPU calculations (unfortunately, fast double-checking is not possible yet).

Task size has been selected to be about 30 minutes on a 1660-class GPU. Since task runtime is proportional to log2(b), first tasks will be completed faster. They'll reach expected length around b=300M and continue to grow slowly until end of project.

Since it'll be first time when Genefer 2.0 will be used in Boinc environment and on many different hosts, all tasks will be fully double-checked.

Known issues

** No graceful error handling **

This program does not tolerates even slightest of GPU errors. If case of any calculation error, program will immediately abort with "Gerbicz failed" message. There are no restarts. Check GPU temperatures, underclock the GPU.

** A problem with multi-GPU systems **

A bug in version 1.00 causes program to always use first GPU in the system. It'll be fixed soon.

Update 1.01 fixed some multi-GPU issues, but it'll work only if your cards are of same type (i.e. all NVidia or all ATI). A combo of NVidia+ATI will not work. Correct fix is more complex. Hopefully it'll be done later.

** Note **

Please avoid running this project on hosts which can interrupt GPU calculations often, especially on slow GPUs. For example, on systems which are configured to run Boinc or GPU tasks "only when user is not active", and user interrupts too often. Currently implemented checkpoint system saves only index of last fully processed candidate, but not a current state of each test. Although each individual test can be short (for example, 2 seconds), there are up to 256 test running in parallel. If a program will be interrupted again within 256*2 seconds, no progress can be recorded.
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