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GIMPS newsletter #11, 26 May, 1997

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The Mersenne Newsletter, issue #11 May 26, 1997

IMPORTANT: New Range Reservation Policy

In the past, I have sent email to those who have been slow in
reporting results from a range they have checked out. Unfortunately,
I am no longer able to do this. It is just too time consuming.

Starting June 1, I will return a range to the available pool if
either of the following occur:
1) No results are reported during a 4 month period.
2) The range is not completed within 8 months.

Hopefully, this will not be a burden to anyone - especially since I
encourage you to send in results once every month or two. As always,
I can make exceptions if you let me know ahead of time.

This policy will make it easier for me to detect people who have
dropped out of the search and will ensure that active testers will
always have the smallest possible ranges to choose from.


Two-and-a-half years ahead of my original schedule, GIMPS has completed
testing all exponents below 1,000,000! Can 2,000,000 be far behind?
My records indicate we are more than 94% of the way there!

Status for exponents below 2,655,000

Since mid-March, we've proved another 10,936 Mersenne numbers composite.
There are now only 10,787 untested exponents remaining below 2,655,000.
We've been so effective at finding composites that the chance of finding
a new Mersenne prime in this range has fallen to 50%.

The time required to finish this range has dropped from
460 Pentium-90 CPU-years to 238.

Status for exponents from 2,655,000 to 5,260,000

Since mid-March, we've proved 7,484 Mersenne numbers composite.
Most of these composite numbers were found by people running the
factoring step. Less than a 1,000 Lucas-Lehmer tests have been run
in this range.

There are now 74,549 exponents left to test. It will take an
estimated 6,233 P-90 CPU years to complete.

Best wishes and good luck to all,
George Woltman