Welcome to the Solar Eclipse Challenge
The fourth Challenge of the 2017 Challenge series is a 3 day challenge to celebrate the Solar eclipse of August 21, 2017. The challenge is being offered on the Generalized Cullen/Woodall Prime Search (LLR) application.
On Monday, August 21, 2017, a total solar eclipse will be visible in totality within a band across the entire contiguous United States. It will only be visible in other countries as a partial eclipse. The previous time a total solar eclipse was visible across the entire contiguous United States was on June 8, 1918.
A solar eclipse occurs when the moon passes between earth and the sun, thereby totally or partly obscuring the image of the sun for a viewer on Earth. A total solar eclipse occurs when the moon's apparent diameter is larger than the sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.
Not since the February 1979 eclipse has a total eclipse been visible from the mainland United States. The path of totality will touch 14 states, though a partial eclipse will be visible in many more states. The event will begin on the Oregon coast as a partial eclipse at 9:06 a.m. PDT on August 21, and will end later that day as a partial eclipse along the South Carolina coast at about 4:06 p.m. EDT. Many total eclipse viewing events are planned http://www.americaneclipse2017.org/eclipse-events/.
To participate in the Challenge, please select only the Generalized Cullen/Woodall Prime Search (LLR) project in your PrimeGrid preferences section. The challenge will begin 20th August 2017 18:00 UTC and end 23rd August 2017 18:00 UTC.
Application builds are available for Linux 32 and 64 bit, Windows 32 and 64 bit and MacIntel. Intel CPUs with AVX capabilities (Sandy Bridge, Ivy Bridge, Haswell, Broadwell, Skylake, Kabylake) will have a very large advantage, and Intel CPUs with FMA3 (Haswell, Broadwell, Skylake, Kabylake) will be the fastest.
ATTENTION: The primality program LLR is CPU intensive; so, it is vital to have a stable system with good cooling. It does not tolerate "even the slightest of errors." Please see this post for more details on how you can "stress test" your computer. Tasks will take ~16 hours on fast/newer computers and 24+ hours on slower/older computers. If your computer is highly overclocked, please consider "stress testing" it. Sieving is an excellent alternative for computers that are not able to LLR. :)
Highly overclocked Haswell, Broadwell, Skylake, or Kabylake (i.e., Intel Core i7, i5, and i3 -4xxx or better) computers running the application will see fastest times. Note that GCW is running the latest FMA3 version of LLR which takes full advantage of the features of these newer CPUs. It's faster than the previous LLR app and draws more power and produces more heat. If you have a Haswell, Broadwell, Skylake, or Kabylake CPU, especially if it's overclocked or has overclocked memory, and haven't run the new FMA3 LLR before, we strongly suggest running it before the challenge while you are monitoring the temperatures.
Please, please, please make sure your machines are up to the task.
Time zone converter:
The World Clock - Time Zone Converter
NOTE: The countdown clock on the front page uses the host computer time. Therefore, if your computer time is off, so will the countdown clock. For precise timing, use the UTC Time in the data section to the left of the countdown clock.
Scores will be kept for individuals and teams. Only tasks issued AFTER 20 August 2017 18:00 UTC and received BEFORE 23 August 2017 18:00 UTC will be considered for credit. We will be using the same scoring method as we currently use for BOINC credits.
A quorum of 2 is NOT needed to award Challenge score - i.e. no double checker. Therefore, each returned result will earn a Challenge score. Please note that if the result is eventually declared invalid, the score will be removed.
At the Conclusion of the Challenge
We kindly ask users "moving on" to ABORT their tasks instead of DETACHING, RESETTING, or PAUSING.
ABORTING tasks allows them to be recycled immediately; thus a much faster "clean up" to the end of an LLR Challenge. DETACHING, RESETTING, and PAUSING tasks causes them to remain in limbo until they EXPIRE. Therefore, we must wait until tasks expire to send them out to be completed.
Please consider either completing what's in the queue or ABORTING them. Thank you. :)
About the Generalized Cullen/Woodall Prime Search
A Cullen number (first studied by Reverend James Cullen in 1905) is a number of the form n * 2^n + 1. A Woodall number (first studied by Allan Cunningham and H.J. Woodall in 1917) is a number of the form n * 2^n - 1.
Generalized Cullen and Woodall numbers are of the form n * b^n + 1 and n * b^n - 1, respectively, where n + 2 > b.
PrimeGrid recently moved its search for Generalized Cullen and Generalized Woodall primes from PRPNet to BOINC. A double-check of all ranges searched by PRPNet has been completed by PrimeGrid, and is continuing on with new work running multiple bases (b values) concurrently and incrementing through n values.
PrimeGrid is sieving to a much larger n than has been previously done. The largest candidates will be in excess of 15,000,000 digits, and will be the same size as the largest candidates in the Seventeen or Bust project.
Once PrimeGrid finds a Generalized Cullen or Woodall on a base, it stops looking for Generalized Cullen or Woodall primes on that base, depending on the type found. For all the current bases, PrimeGrid will initially be searching only for Generalized Cullen Primes. For detail about the bases PrimeGrid will be searching (and has searched), you can go here: http://www.primegrid.com/forum_thread.php?id=3008&nowrap=true#30718.
In addition to having found the largest known Cullen prime http://primes.utm.edu/primes/page.php?id=89536 and largest known Woodall prime http://primes.utm.edu/primes/page.php?id=83407, PrimeGrid has found the largest known Generalized Cullen prime, http://primes.utm.edu/primes/page.php?id=122349 and the 4th largest known Generalized Woodall prime http://primes.utm.edu/primes/page.php?id=98862.
For more information on Generalized Cullen and Woodall Numbers, you can go here: http://primes.utm.edu/top20/page.php?id=42 and here: http://primes.utm.edu/top20/page.php?id=45.
What is LLR?
The Lucas-Lehmer-Riesel (LLR) test is a primality test for numbers of the form N = k*2^n − 1, with 2^n > k. Also, LLR is a program developed by Jean Penne that can run the LLR-tests. It includes the Proth test to perform +1 tests and PRP to test non base 2 numbers. See also:
(Edouard Lucas: 1842-1891, Derrick H. Lehmer: 1905-1991, Hans Riesel: 1929-2014).