Cube Challenge 3^3 - 27th May till 3rd June 2017

Announced is a challenge at the 27 prime search project from the 27th May till 3rd of June to celebrate cubes and the number 27 in particular.
We will start at 12:00 UTC and finish at 12:00 UTC one week later.

In geometry, a cube is a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex.
The cube is the only regular hexahedron and is one of the five Platonic solids. It has 6 faces, 12 edges, and 8 vertices.

In arithmetic and algebra, the cube of a number n is its third power: the result of the number multiplied by itself twice:
n^3 = n × n × n.
It is also the number multiplied by its square:
n^3 = n × n^2.

A cube number, or a perfect cube, or sometimes just a cube, is a number which is the cube of an integer. The perfect cubes up to 60^3 are (sequence A000578 in the OEIS). Subject of our challenge, 27, is the 4th number in this sequence.

Determination of the cubes of large numbers was very common in many ancient civilizations. Mesopotamian mathematicians created cuneiform tablets with tables for calculating cubes and cube roots by the Old Babylonian period (20th to 16th centuries BC).Cubic equations were known to the ancient Greek mathematician Diophantus.Hero of Alexandria devised a method for calculating cube roots in the 1st century CE. Methods for solving cubic equations and extracting cube roots appear in The Nine Chapters on the Mathematical Art, a Chinese mathematical text compiled around the 2nd century BCE and commented on by Liu Hui in the 3rd century CE. The Indian mathematician Aryabhata wrote an explanation of cubes in his work Aryabhatiya. In 2010 Alberto Zanoni found a new algorithm to compute the cube of a long integer in a certain range, faster than squaring-and-multiplying.

More about the 27121 prime search can be found here. News and infos about the PRPNet client can be found here.

To take part, you have to activate the following lines in prpclient.ini:

The Challenge has begun.
Grebuloner and The_Knights_Who_Say_Ni! have the early lead.

I'm in! Took a bit of playing around, but I got multithreading to work using the batch file hack (Thanks, Roger.) Tasks are taking about 50 minutes on my Haswell with 4 of 4 cores.
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My lucky number is 75898⁵²⁴²⁸⁸+1

I'm in! Took a bit of playing around, but I got multithreading to work using the batch file hack (Thanks, Roger.) Tasks are taking about 50 minutes on my Haswell with 4 of 4 cores.

Where is info for doing this?

Couldn't get multithreading to work, so just ran some single core clients instead.

A few hours ago was checking one of my clients and it flashed up highlighted that it had found a prime but when I go to http://prpnet.primegrid.com:12006/user_primes.html page it says it is "hidden".

How do I unhide it please?

That candidate is not prime. Mike and I got matching results:

Mine:
cllr64 -d -t4 -q"27*2^6560020-1"
Starting Lucas Lehmer Riesel prime test of 27*2^6560020-1
Using AVX FFT length 384K, Pass1=384, Pass2=1K, 4 threads
V1 = 5 ; Computing U0...done.
27*2^6560020-1 is not prime. LLR Res64: 94216F6B9DFBB58B Time : 3816.986 sec.

Mike's:
27*2^6560020-1 is not prime. LLR Res64: 94216F6B9DFBB58B Time : 2939.457 sec.

Any "prime" where c == -1 is always suspicious. The algorithm used by the LLR program returns a prime result if there are hardware problems. When c == 1 and there are errors the residue shows as 0000000000000001. For that reason, our BOINC validator requires three matching results to believe 0000000000000001 and even then it'll email me so that I can test manually. There are 13 false primes with c == -1 in the BOINC system at the moment.

I'll fix the results and remove the "prime" record. I think I have a program to do it all for me - it involves changing a half dozen tables.

LLR is based on the same code as Prime95, and Prime95 is used as a stress test by overclockers because it pushes the CPU so hard. The apps here are significantly tougher than most programs. If there's any instability at all in your system, it will show up here.

If you just put in new memory, my guess would be that's where the problem is.
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My lucky number is 75898⁵²⁴²⁸⁸+1

WU's completed so far:
27th May 375 (only some of these counted for the challenge)
28th May 691
29th May 883
30th May 1,002
31st May 1,032
A steady increase to be sure.
Leading edge of the search has increased from 6,525,272 to 6,587,564 on both the plus and minus sides. Goal is to get to 6.6M.

The Challenge has ended. Congratulation to Grebuloner and The_Knights_Who_Say_Ni!

The top of the challenge rankings is as follows:

permanent link to the stats: http://u-g-f.de/PRPNet/2017_06_27_Challenge.html
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Sysadm@Nbg
my current lucky number: 3749*2^1555697+1
PSA-PRPNet-Stats-URL: http://u-g-f.de/PRPNet/