How GIMPS Works

This page describes what you will need to participate in GIMPS and how it works on your computer. This page is aimed at people with Intel-compatible personal computers, although in many cases it is possible for UNIX and Mac users to participate as well.

In brief, you need:

1. a relatively modern computer - though very old computers can still be useful to help other computers find primes.
2. your computer on and running more often than off - at least most of the time - it's OK to go on holidays, vacations, etc.
3. time and patience - testing for a prime can take weeks even on the fastest computers and months on very old computers.
4. an Internet connection available at least once every two months - more often is preferred, weekly or daily is ideal .

GIMPS requires a modern PC that is on most of the time. The program runs at the lowest possible priority. You should not see any impact on your system's performance. The program will use about 32MB of memory and about 50MB of disk space. WARNING: Running the program continuously will use about 40 watts of additional power, about the same as an energy-saving compact florescent lamp - your electric bill will go up just a little bit.

Most importantly, you will need a lot of patience. Roughly speaking it will take about a month to run a single primality test - visit the benchmark page for a more accurate estimate on your computer.

If you've decided you have a powerful enough computer and enough patience to stick with the project, then visit the download page for instructions on downloading, installing, and starting the program.

The program talks to PrimeNet, a central server on the Internet, to get work to do and report results. The program communicates using the HTTP protocol and may require a little extra configuration to get through some firewalls. The program only sends a few hundred bytes every week. Thus, there is no impact on your network performance. The program does not require a continuous Internet connection and if properly configured will not automatically dial out to establish an Internet connection.

There are several types of work assigned by the server. 1.4GHz and faster computers get first-time primality tests. These tests require the most work and have the best chance of finding a new Mersenne prime. Computers between 1GHz and 1.4 GHz usually get double-check assignments. These assignments do not take as long and can find a Mersenne prime only if the original test had a problem. The slowest computers are usually assigned factoring work. This helps by eliminating some exponents for the faster computers though it will not find new primes.  For more details about this systematic research methodology used by GIMPS, see The Math page.

Every half hour the program saves its state so that if there is a computer crash you will lose at most a half-hour of work. All temporary files and program settings are conveniently stored in the same folder as the program.

Before you complete your assignment, the program will get more work to do from PrimeNet. This will assure that your computer has a continuous supply of work. When the work assignment is completed the program returns one of several possible types of results to PrimeNet, then proceeds with the next work assignment task.

If you are lucky enough to find a new Mersenne prime, the program notifies the server and optionally emits a continuous sound to notify you of the happy news! There may be a cash research discovery award for your new prime!

Last updated: November 30, 2008