Welcome to the Halloween Challenge!
The seventh Challenge of the 2018 Challenge series is a 7 day challenge to celebrate Halloween. The challenge is being offered on the Woodall Prime Search (LLR) application.
Halloween or Hallowe'en (a contraction of Hallows' Evening), also known as Allhalloween, All Hallows' Eve, or All Saints' Eve, is a celebration observed in a number of countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. It begins the three-day observance of Allhallowtide, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the faithful departed.
It is widely believed that many Halloween traditions originated from ancient Celtic harvest festivals, particularly the Gaelic festival Samhain; that such festivals may have had pagan roots; and that Samhain itself was Christianised as Halloween by the early Church. Some believe, however, that Halloween began solely as a Christian holiday, separate from ancient festivals like Samhain.
Halloween activities include trick-or-treating (or the related guising), attending Halloween costume parties, carving pumpkins into jack-o'-lanterns, lighting bonfires, apple bobbing, divination games, playing pranks, visiting haunted attractions, telling scary stories, and watching horror films. In many parts of the world, the Christian religious observances of All Hallows' Eve, including attending church services and lighting candles on the graves of the dead, remain popular, although elsewhere it is a more commercial and secular celebration. Some Christians historically abstained from meat on All Hallows' Eve, a tradition reflected in the eating of certain vegetarian foods on this vigil day, including apples, potato pancakes, and soul cakes.
To participate in the Challenge, please select only the Woodall Prime Search LLR (WOO) project in your PrimeGrid preferences section. The challenge will begin 24th October 2018 23:59:59 UTC and end 31st October 2018 23:59:59 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, Kaby Lake, Coffee Lake) will have a very large advantage, and Intel CPUs with FMA3 (Haswell, Broadwell, Skylake, Kaby Lake, Coffee Lake) 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 on one CPU core will take ~2 days on fast/newer computers and 7+ days 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, Kaby Lake or Coffee Lake (i.e., Intel Core i7, i5, and i3 -4xxx or better) computers running the application will see fastest times. Note that WOO 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, Kaby Lake or Coffee Lake 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.
Multi-threading optimisation instructions
Those looking to maximise their computer's performance during this challenge, or when running LLR in general, may find this information useful.
- Your mileage may vary. Before the challenge starts, take some time and experiment and see what works best on your computer.
- If you have an Intel CPU with hyperthreading, either turn off the hyperthreading in the BIOS, or set BOINC to use 50% of the processors.
- If you're using a GPU for other tasks, it may be beneficial to leave hyperthreading on in the BIOS and instead tell BOINC to use 50% of the CPU's. This will allow one of the hyperthreads to service the GPU.
- Use LLR's multithreaded mode. It requires a little bit of setup, but it's worth the effort. Follow these steps:
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 at the very top, above the countdown clock.
Scores will be kept for individuals and teams. Only tasks issued AFTER 24th October 2018 23:59:59 UTC and received BEFORE 31st October 2018 23:59:59 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 Woodall Prime Search
Woodall Numbers (sometimes called Cullen numbers 'of the second kind') are positive integers of the form Wn = n*2^n-1, where n is also a positive integer greater than zero. Woodall numbers that are prime are called Woodall primes (or Cullen primes of the second kind).
The Woodall numbers Wn are primes for the following n:
2, 3, 6, 30, 75, 81, 115, 123, 249, 362, 384, 462, 512, 751, 822, 5312, 7755, 9531, 12379, 15822, 18885, 22971, 23005, 98726, 143018, 151023, 667071, 1195203, 1268979, 1467763, 2013992, 2367906, 3752948, and 17016602 and composite for all other n less than 17337441.
It is conjectured that there are infinitely many such primes. Currently, PrimeGrid is testing for Woodall primes in the n=17M - n=18M level (M=mega, 10^6). The last 4 Woodall primes found by PrimeGrid are:
2013992*2^2013992−1 (Lasse Mejling Andersen): official announcement | Prime Pages Entry
2367906*2^2367906−1 (Stephen Kohlman): official announcement | Prime Pages Entry
3752948*2^3752948−1 (Matthew J. Thompson): official announcement | Prime Pages Entry
17016602*2^17016602−1 (Diego Bertolotti): official announcement | Prime Pages Entry
For more information on Woodall numbers, please visit the following sites:
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).