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.

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