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GIMPS newsletter #15, 3 April, 1999

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The Mersenne Newsletter, issue #15 April 3, 1999

Serious Bug Found in Version 17
Version 17 was released a few months ago to allow double-checking
previously tested exponents. Since about 1 in 100 previous tests are
incorrect, you can still find a Mersenne prime by double-checking.
This is the perfect chore for slower Pentiums. You don't have to wait
several months for each Lucas-Lehmer test to complete.

Unfortunately, a bug was introduced that affected tests on exponents
above 4,194,304. Download version 18 immediately at or

This bug affected about 11,000 out of 59,000 reported results above 4,194,304.
All results produced by version 16 are OK. All results that were started
by version 16 and completed by version 17 are OK. All factoring and
double-checking work is OK.

After upgrading to version 18, you may get error messages that look like this:
Error reading intermediate file: p6180331
Renaming intermediate file q6180331 to p6180331.
Error reading intermediate file: p6180331
This is normal. Prime95 must discard incorrect version 17 save files.

To those that have been using version 17 to test exponents above 4,194,304
I offer my sincerest apologies. I know that upgrading will be very
inconvenient and it will be disheartening to lose months of work. Sorry.

On the bright side, perhaps one of the 11,000 affected exponents will
turn out to be prime allowing someone to win a big prize described below!

EFF Announces $50,000 Prize For Finding Million Digit Prime!!!
On March 31, the Electronic Frontier Foundation announced a $50,000
prize to be awarded to the first person to find a million digit
prime number! The details are available at

Since GIMPS is now testing numbers well in excess of 1 million digits,
some lucky GIMPS member could very well win this prize!

If you are using business computers, a friend's computer, or a
co-worker's computer, I recommend you discuss how the $50,000 prize
would be divided should you be the lucky winner. Note that according
to the contest rules, you could be denied the prize if you have not
legally obtained permission to use the computer that finds the prime number.

In light of the EFF anouncement, the $1,500 prize fund for discovering
the 38th Mersenne prime has been discontinued.

Future Newsletters
I will no longer email the Mersenne newsletter to every GIMPS user. Instead,
there will be three ways to get future newsletters:
1) Online at Check periodically for
new editions.
2) Subscribe to the Mersenne mailing list. I will send future newsletters
to the mailing list.
3) Use the web form at to request
having future newsletters emailed to you. A link to the web form will
also be available from

Since the last newsletter 10 months ago, many thousands have joined GIMPS!
There are now more than 8,000 people involved in the search. Welcome to all
the new searchers! I'm sorry your first newsletter had to announce bad
news. This is the first serious setback for GIMPS in its three and a half
year history.

PrimeNet Server news
Link your Top Producer's Page account name to your home page!
Check out the people, teams, businesses and schools behind the
top CPU time accounts at,
and add your own page link! upgraded the GIMPS Internet PrimeNet Server on
9 February to PrimeNet 4.0, a powerful new system built on their
new v4 Internet computing technology. The 4.0 server offers
substantial reliability improvements and an order of magnitude
better performance and feature integration flexibility.

If you are using the RPC protocol, please use the faster HTTP
protocol instead. You can select this option in the version 18
Windows software in the Test/PrimeNet dialog box. MPrime and
PrimeOS2 already use HTTP.

To get your full PrimeNet account report without a password
(for example, to use in a web page), email
with your request.

The thoughtful community of GIMPS participants
continues to grow. The PrimeNet virtual supercomputer is
currently producing over 560 billion floating point operations
per second, which puts it among the top 10 most powerful systems
in the world. This amazing strength arises from the spare CPU
time from your computer and some 15,000 others on about 8,800
individual, team and business accounts. For more on's PrimeNet system and related projects, see and, or email

Finally, if PrimeNet emails you a confirmation that it received
a Mersenne prime from your computer, please remember worldwide
academic research discovery rules apply. Please contact me
immediately at, and do not communicate the
discovery until we have verified it on a conventional Cray
supercomputer. I will help you work with EFF to collect your

For other network, server or PrimeNet account related questions,
please email Scott Kurowski's team at

ECM factoring
The program now lets you find factors of small Mersenne numbers using the
Elliptic Curve Method. Mathematicians are interested in completely factoring
Mersenne numbers as well as finding new Mersenne primes. If this interests
you, visit http:\\\ecm.htm for more details. To date we have
discovered 16 new Cunningham factors, including Conrad Curry's largest factor
ever found using ECM.

New email address
My new email address is My old address,, still works. In fact the new address simply forwards
mail to the magicnet address. However, should I ever change ISPs the new
address will forward my mail to the appropriate place.

In the ten months since the last newsletter GIMPS as accomplished
the following milestones:

* Double-checking proves M(1398269) is the 35th Mersenne prime.
* All exponents below M(2976221) tested at least once.
* All exponents below M(3021377) tested at least once.
* All Mersenne numbers less than a million digits tested at least once.

We have completed first-time Lucas-Lehmer tests on about 45,000 Mersenne
numbers. Of these 45,000 numbers tested, we expected to find one
Mersenne prime. We've been a bit unlucky.

However, there are still 396,543 exponents left to test below 20,500,000.
It will only take us 534,493 P-90 CPU years to test exponents and we expect
to find 3.71 Mersenne primes. At Primenet's current rate, we expect to
find one Mersenne Prime this year.

You can watch the hourly progress of the search on the server's
status page at

Once again, I'm sorry about the version 17 bug. Best wishes and good luck
in the future. Hopefully someone will soon find the 38th Mersenne prime
and collect a nice prize! And I can write a more upbeat newsletter!


George Woltman


Scott Kurowski