Great Internet Mersenne Prime Search

The Great Internet Mersenne Prime Search (GIMPS) is a collaborative project of volunteers who use freely available software to search for Mersenne prime numbers.

Not to be confused with GIMP.
GIMPS logo

GIMPS was founded in 1996 by George Woltman, who also wrote the Prime95 client and its Linux port MPrime. Scott Kurowski wrote the back end PrimeNet server to demonstrate distributed computing software by Entropia, a company he founded in 1997. GIMPS is registered as Mersenne Research, Inc. with Kurowski as Executive Vice President and board director. GIMPS is said to be one of the first large scale distributed computing projects over the Internet for research purposes.[1]

As of December 2018, the project has found a total of seventeen Mersenne primes, fifteen of which were the largest known prime number at their respective times of discovery. The largest known prime as of December 2018 is 282,589,933 − 1 (or M82,589,933 for short) and was discovered on December 7, 2018 by Patrick Laroche.[2]

The project relies primarily on the Lucas–Lehmer primality test[3] as it is an algorithm that is both specialized for testing Mersenne primes and particularly efficient on binary computer architectures. There is also a trial division phase, used to rapidly eliminate many Mersenne numbers with small factors. Pollard's p − 1 algorithm is also used to search for smooth factors. In 2017, GIMPS adopted the Fermat primality test as an alternative option for primality testing.

History

The project began in early January 1996,[4][5] with a program that ran on i386 computers.[6][7] The name for the project was coined by Luther Welsh, one of its earlier searchers and the co-discoverer of the 29th Mersenne prime.[8] Within a few months, several dozen people had joined, and over a thousand by the end of the first year.[7][9] Joel Armengaud, a participant, discovered the primality of M1,398,269 on November 13, 1996.[10]

Status

As of May 2020, GIMPS has a sustained average aggregate throughput of approximately 1.17 PetaFLOPS (or PFLOPS).[11] In November 2012, GIMPS maintained 95 TFLOPS,[12] theoretically earning the GIMPS virtual computer a rank of 330 among the TOP500 most powerful known computer systems in the world.[13] The preceding place was then held by an 'HP Cluster Platform 3000 BL460c G7' of Hewlett-Packard.[14] As of November 2014 TOP500 results, these old GIMPS numbers would no longer make the list.

Previously, this was approximately 50 TFLOPS in early 2010, 30 TFLOPS in mid-2008, 20 TFLOPS in mid-2006, and 14 TFLOPS in early 2004.

Software license

Although the GIMPS software's source code is publicly available,[15] technically it is not free software, since it has a restriction that users must abide by the project's distribution terms.[16] Specifically, if the software is used to discover a prime number with at least 100,000,000 decimal digits, the user will only win $50,000 of the $150,000 prize offered by the Electronic Frontier Foundation.[16][17]

Third-party programs for testing Mersenne numbers, such as Mlucas and Glucas (for non-x86 systems), do not have this restriction.

GIMPS also "reserves the right to change this EULA without notice and with reasonable retroactive effect."[16]

Primes found

All Mersenne primes are of the form Mp = 2p − 1, where p is a prime number itself. The smallest Mersenne prime in this table is 21398269 − 1.

The first column is the rank of the Mersenne prime in the (ordered) sequence of all Mersenne primes;[18] GIMPS has found all known Mersenne primes beginning with the 35th.

#Discovery datePrime MpDigits countProcessor
35November 13, 1996M1398269420,921Pentium (90 MHz)
36August 24, 1997M2976221895,932Pentium (100 MHz)
37January 27, 1998M3021377909,526Pentium (200 MHz)
38June 1, 1999M69725932,098,960Pentium (350 MHz)
39November 14, 2001M134669174,053,946AMD T-Bird (800 MHz)
40November 17, 2003M209960116,320,430Pentium (2 GHz)
41May 15, 2004M240365837,235,733Pentium 4 (2.4 GHz)
42February 18, 2005M259649517,816,230Pentium 4 (2.4 GHz)
43December 15, 2005M304024579,152,052Pentium 4 (2 GHz overclocked to 3 GHz)
44September 4, 2006M325826579,808,358Pentium 4 (3 GHz)
45September 6, 2008M3715666711,185,272Intel Core 2 Duo (2.83 GHz)
46June 4, 2009M4264380112,837,064Intel Core 2 Duo (3 GHz)
47August 23, 2008M4311260912,978,189Intel Core 2 Duo E6600 CPU (2.4 GHz)
48[†]January 25, 2013M5788516117,425,170Intel Core 2 Duo E8400 @ 3.00 GHz
49[†]January 7, 2016M7420728122,338,618Intel Core i7-4790
50[†]December 26, 2017M7723291723,249,425Intel Core i5-6600
51[†]December 7, 2018M82589933[‡]24,862,048Intel Core i5-4590T

^ † As of June 21, 2020, 50,740,883 is the largest exponent below which all other prime exponents have been checked twice, so it is not verified whether any undiscovered Mersenne primes exist between the 47th (M43112609) and the 51st (M82589933) on this chart; the ranking is therefore provisional. Furthermore, 91,435,237 is the largest exponent below which all other prime exponents have been tested at least once, so all Mersenne numbers below the 51st (M82589933) have been tested.[19]

^ ‡ The number M82589933 has 24,862,048 decimal digits. To help visualize the size of this number, if it were to be saved to disk, the resulting text file would be nearly 25 megabytes long (most books in plain text format clock in under two megabytes). A standard word processor layout (50 lines per page, 75 digits per line) would require 6,629 pages to display it. If one were to print it out using standard printer paper, single-sided, it would require approximately 14 reams of paper.

Whenever a possible prime is reported to the server, it is verified first before it is announced. The importance of this was illustrated in 2003, when a false positive was reported to possibly be the 40th Mersenne prime but verification failed.[20]

The official "discovery date" of a prime is the date that a human first noticed the result for the prime, which may differ from the date that the result was first reported to the server. For example, M74207281 was reported to the server on September 17, 2015, but the report was overlooked until January 7, 2016.[21]

See also

References
  1. "Volunteer computing". BOINC. Retrieved 8 October 2012.
  2. "GIMPS Project Discovers Largest Known Prime Number: 282,589,933-1". Mersenne Research, Inc. 21 December 2018. Retrieved 21 December 2018.
  3. What are Mersenne primes? How are they useful? - GIMPS Home Page
  4. The Mersenne Newsletter, Issue #9. Retrieved 2011-10-02. Archived 2012-02-06 at the Wayback Machine
  5. "mersenneforum.org - View Single Post - Party on! GIMPS turns 10!!!". www.mersenneforum.org. Retrieved 22 December 2018.
  6. Woltman, George (February 24, 1996). "The Mersenne Newsletter, issue #1" (txt). Great Internet Mersenne Prime Search (GIMPS). Retrieved 2009-06-16.
  7. Woltman, George (January 15, 1997). "The Mersenne Newsletter, issue #9" (txt). GIMPS. Retrieved 2009-06-16.
  8. The Mersenne Newsletter, Issue #9. Retrieved 2009-08-25.
  9. Woltman, George (April 12, 1996). "The Mersenne Newsletter, issue #3" (txt). GIMPS. Retrieved 2009-06-16.
  10. Woltman, George (November 23, 1996). "The Mersenne Newsletter, issue #8" (txt). GIMPS. Retrieved 2009-06-16.
  11. PrimeNet Activity Summary, GIMPS, retrieved 2020-05-03
  12. PrimeNet Activity Summary, GIMPS, retrieved 2012-04-05
  13. "TOP500 - November 2012". Retrieved 22 November 2012.
  14. TOP500 per November 2012; HP BL460c with 95.1 TFLOP/s (R max)."TOP500 - Rank 329". Retrieved 22 November 2012.
  15. "Software Source Code". Mersenne Research, Inc. Retrieved March 16, 2013.
  16. EFF Cooperative Computing Awards, Electronic Frontier Foundation, retrieved 2011-09-19
  17. "GIMPS List of Known Mersenne Prime Numbers". Mersenne Research, Inc. Retrieved 2018-01-03.
  18. "GIMPS Milestones". Mersenne Research, Inc. Retrieved 2020-06-12.
  19. "M40, what went wrong? - Page 11 - mersenneforum.org". mersenneforum.org. Retrieved 22 December 2018.
  20. "GIMPS Project Discovers Largest Known Prime Number". January 19, 2016.
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