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11)
Message boards :
Number crunching :
Oktoberfest Challenge
(Message 133949)
Posted 1027 days ago by Roger
The results are final!
Well done to Robish for finding the first ever AP27!
224584605939537911+81292139*23#*n for n=0..26
Top 3 individuals:
1: Jack Hiker
2: tng*
3: vaughan
Top 3 teams:
1: Czech National Team
2: Sicituradastra.
3: TeAm AnandTech
Congratulations to the winners, and well done to everyone who participated.
See you at the 50 years First ARPANET Connection Challenge!

12)
Message boards :
Number crunching :
World Maths Day Challenge
(Message 133708)
Posted 1033 days ago by Roger
Yves Gallot:
"Historically, there are 3 searches for Fermat divisors:
 The small divisors (n < 29): the Fermat numbers can be computed then we apply a factorization method. ECM is the fastest algorithm and the GIMPS is searching for these divisors https://www.mersenne.org/report_ecm/. The main targets are F_{20} and F_{24} (without known factor).
 The medium size divisors: we don't check if k.2^{n}+1 is prime (too slow) but just apply a quick sieve on it and test if there exists m such that 2^{2m} = 1 (mod k.2^{n}+1). In 2000, Leonid Durman wrote Fermat.exe and found many factors with it. FermatSearch was based on it. The main targets are F_{33}, F_{34} & F_{35} (prime or composite?).
 The big divisors: we search for large primes and check if they divide a Fermat number. Historically, Proth.exe, PFGW, LLR, PrimeGrid. The main target is the largest known factor.
The border between FermatSearch and (today) PrimeGrid was never defined but I think that the main difference is that FermatSearch is searching for Fermat factors and PrimeGrid is searching for primes. Then k < k_{max} for PrimeGrid is certainly a better choice than n > n_{min}. We search for fixed k and varying n and FermatSearch is searching for fixed n and varying k.
A database for primes of the form k.2^{n}+1 such that k < k_{max} doesn't exist. http://www.prothsearch.com/ contains useful information but there is no true database (at least a huge tabulated ASCII file). Because FermatSearch is searching for Fermat divisors and not primes, only PrimeGrid can create it today. The properties of the primes k.2^{n}+1 are important and a database is useful for finding them."

13)
Message boards :
Number crunching :
World Maths Day Challenge
(Message 133692)
Posted 1033 days ago by Roger
I updated the Welcome post. k=19683 up to n=4M is now complete.
PPSDIV is now 5% complete in total. Leading edge now at n=4,359,742.
7 hours to go, and counting.

14)
Message boards :
Project Staging Area :
Is it technically possible to move factorial and primorial searches to BOINC?
(Message 133566)
Posted 1037 days ago by Roger
Doublechecks don't need BOINC, although BOINC automates the process.
Sieving further is certainly doable.
A better question is why to port 'orial's to BOINC?
Would do more work on BOINC, but at the cost of existing subprojects.

15)
Message boards :
Number crunching :
World Maths Day Challenge
(Message 133388)
Posted 1043 days ago by Roger
Welcome to the World Maths Day Challenge
The seventh Challenge of the 2019 Challenge series is a 5 day challenge to celebrate World Maths Day. The challenge is being offered on the new Fermat Divisor Search (PPSDIV) (LLR) application.
Celebrated on October 15th each year, World Maths Day encourages students globally to take a break from standard math lessons giving them the opportunity to enjoy the beauty of mathematics by participating in mathsthemed competitions, quizzes and games. It focuses on making mathematics interesting while also giving them an opportunity to win prizes and scholarships.
To participate in the Challenge, please select only the Fermat Divisor Search LLR (PPSDIV) project in your PrimeGrid preferences section. The challenge will begin 10th October 2019 18:00 UTC and end at 15th October 2019 18:00 UTC.
Application builds are available for Linux 32 and 64 bit, Windows 32 and 64 bit and MacIntel. Intel CPUs with FMA3 capabilities (Sandy Bridge, Ivy Bridge, Haswell, Broadwell, Skylake, Kaby Lake, Coffee Lake) will have a very large advantage, and Intel CPUs with dual AVX512 (certain recent Intel SkylakeX and Xeon CPUs) 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 hours on fast/newer computers and 5 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, 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 PPSDIV is running the latest AVX512 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 certain recent Intel SkylakeX and Xeon CPUs, especially if it's overclocked or has overclocked memory, and haven't run the new AVX512 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.
Multithreading 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.
 The new multithreading system is now live. This will allow you to select multithreading from the project preferences web page. No more app_config.xml. It works like this:
 In the preferences selection, there are selections for "max jobs" and "max cpus", similar to the settings in app_config.
 Unlike app_config, these two settings apply to ALL apps. You can't chose 1 thread for SGS and 4 for SoB. When you change apps, you need to change your multithreading settings if you want to run a different number of threads.
 There will be individual settings for each venue (location).
 This will eliminate the problem of BOINC downloading 1 task for every core.
 The hyperthreading control isn't possible at this time.
 The "max cpus" control will only apply to LLR apps. The "max jobs" control applies to all apps.
 If you want to continue to use app_config.xml for LLR tasks, you need to change it if you want it to work. Please see this message for more information.
 t1 or t2 is best on most computers. On older hardware (i7950 for example), it is now best to run t4.
 Some people have observed that when using multithreaded LLR, hyperthreading is actually beneficial. We encourage you to experiment and see what works best for you.
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.
Scoring Information
Scores will be kept for individuals and teams. Only tasks issued AFTER 10th October 2019 18:00 UTC and received BEFORE 15th October 2019 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 Fermat Divisor Search
In mathematics a Fermat number, named after Pierre de Fermat who first studied them, is a positive integer of the form F_{n} = 2^{2n}+1, where n is a nonnegative integer.
The first few Fermat numbers are 3, 5, 17, 257, 65537, 4294967297, 18446744073709551617, … (sequence A000215 in the OEIS).
Only five Fermat primes are known, and the Fermat numbers grow so quickly that it may be years before the first undecided case: F_{33} = 2^{233}+1 is shown prime or composite  unless we luck onto a divisor. Ever since Euler found the first Fermat divisor (divisor of a Fermat composite), factorers have been collecting these rare numbers.
The largest known prime Fermat divisor is the megaprime 193 * 2^{3329782}+1, discovered by PrimeGrid in 2014, which divides F_{3329780} = 2^{23329780}+1. Will we break this record during the challenge?
Euler showed that every divisor of F_{n} (n greater than 2) must have the form k*2^{n+2}+1 for some integer k. For this reason, when we find a large prime of the form k*2^{n}+1 (with k small), we usually check to see if it divides a Fermat number. The probability of the number k*2^{n}+1 dividing any Fermat number appears to be 1/k.
Any prime Generalised Fermat Number F_{b,n} = b^{2n}+1 (with b an integer greater than one) is called a generalised Fermat prime (because they are Fermat primes in the special case b=2), Ribenboim (1996).
Riesel (1994) further generalised by defining Extended Generalised Fermat Numbers xGF_{n,a,b} = a^{2n}+b^{2n}.
In the Fermat Divisor Search we focus on special k's that are either small (generally gives high chance of dividing a Fermat number) or have special properties that makes them attractive.
First we'll first search k=19683 up to n=4M, (now complete).
Then five additional k's, 1323 (even n only), 2187 (even n only), 3125, 3267 (even n only) and 3375, up to n=3.322M, (now complete).
Finally 5<=k<=49 up to n=9M.
See also:
What is LLR?
The LucasLehmerRiesel (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 LLRtests. It includes the Proth test to perform +1 tests and PRP to test non base 2 numbers. See also: (Edouard Lucas: 18421891, Derrick H. Lehmer: 19051991, Hans Riesel: 19292014).

16)
Message boards :
Number crunching :
Oktoberfest Challenge
(Message 133162)
Posted 1050 days ago by Roger
Wow! So awesome. We can all bask in the glory.
Congrats to the lucky finder.
Beers are on me.
Cheers!

17)
Message boards :
Number crunching :
Oktoberfest Challenge
(Message 133071)
Posted 1052 days ago by Roger
Munich's Oktoberfest has officially opened, with Mayor Dieter Reiter tapping the keg.
Fast start to the Challenge. Already 207 Users and 55 Teams have returned tasks.
Last AP26 was found in November 2018:
https://www.primegrid.com/forum_thread.php?id=7012&nowrap=true#122589
Remember to check you AP Discoveries.
Give a shout out if you find any big ones.
Cheers!

18)
Message boards :
News :
Oktoberfest Challenge!
(Message 132967)
Posted 1055 days ago by Roger
From September 21st, 2019 Primegrid will be running an AP27 Challenge to celebrate Oktoberfest! The world's biggest Volkfest is held annually in Munich, Bavaria, Germany, with more than six million people from around the world attending.
The Challenge starts at 11:00 UTC and ends 5 days later on 26th September at 11:00 UTC. Work units from the AP27 project, which are downloaded and completed during the challenge will count towards your challenge score.
The last AP26 was found on 17th November 2018. Can we find an AP27 during the Challenge?
For more information and discussion, please head over to the official challenge thread: http://www.primegrid.com/forum_thread.php?id=8764
Good luck!

19)
Message boards :
Number crunching :
Oktoberfest Challenge
(Message 132831)
Posted 1059 days ago by Roger
Welcome to the Oktoberfest Challenge!
The sixth Challenge of the 2019 Challenge series is a 5 day challenge to celebrate Oktoberfest. The challenge will be running on the AP27 Search.
Oktoberfest is the world's largest Volksfest (beer festival and travelling funfair). Held annually in Munich, Bavaria, Germany, it is a 16 to 18day folk festival running from mid or late September to the first weekend in October, with more than six million people from around the world attending the event every year. Locally, it is often called the Wiesn, after the colloquial name for the fairgrounds, Theresa's meadows (Theresienwiese). The Oktoberfest is an important part of Bavarian culture, having been held since the year 1810. Other cities across the world also hold Oktoberfest celebrations that are modelled on the original Munich event.
During the event, large quantities of Oktoberfest Beer are consumed: during the 16day festival in 2013, for example, 7.7 million litres were served. Visitors also enjoy numerous attractions, such as amusement rides, sidestalls, and games. There is also a wide variety of traditional foods available.
This year Oktoberfest will start on Saturday, September 21st. The Schottenhamel tent will be the place to be if you want to catch the official opening ceremonies. At noon, the Mayor of Munich will have the honor of tapping the first keg of Oktoberfest beer. Once the barrel has been tapped, all visitors will then be allowed to quench their thirst. The festival will go until Sunday, October 6th.
Arithmetic progressions
In mathematics, an arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. For instance, the sequence 5, 7, 9, 11, 13, 15 … is an arithmetic progression with common difference of 2.
An arithmetic progression of primes is a sequence of primes with a common difference between any two successive numbers in the sequence. For example 3, 7, 11 is an arithmetic progression of 3 primes with a common difference of 4.
For an arithmetic progression (AP) of primes, APk is k primes of the form p + d*n for some d (the common difference between the primes) and k consecutive values of n. The above AP3 is 3 + 4*n for n=0,1,2.
How to Participate?
To participate in the Challenge, please select only the AP 27 (AP27) project in your PrimeGrid preferences section. The challenge will begin 21st September 2019 11:00 UTC and end 26th September 2019 11:00 UTC. Application builds are available for Linux , Windows and MacIntel CPUs and GPUs. CPU apps are only available for 64 bit CPUs. High end Nvidia GPUs will have a very large advantage.
Tasks will take ~29 hours on average for CPUs and ~75 minutes on average for GPUs. If your computer is highly overclocked, please consider "stress testing" it. If you haven't run the AP app before, we strongly suggest running it before the challenge while you are monitoring the temperatures. You don't want to turn your machine into a meteor!
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.
Scoring Information
Scores will be kept for individuals and teams. Only tasks issued AFTER 21 September 2019 11:00 UTC and received BEFORE 26 September 2019 11:00 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 a 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. :)
For more information about the AP27 search, please visit these links:
 AP 27 Search
 AP 26 Search
 http://en.wikipedia.org/wiki/Arithmetic_progression
 Jens Kruse Andersen's Primes in Arithmetic Progression Records

20)
Message boards :
News :
World Maths Day Challenge
(Message 132794)
Posted 1061 days ago by Roger
Announcing a new Challenge slot! To celebrate World Maths Day, and our new PPSDIV subproject, we'll be running a 5 day Challenge from 10th October 18:00 UTC until 15th October 18:00 UTC. Other Challenge dates are unaffected.
The Fermat Divisor search is especially designed to have a better chance of finding a Fermat Divisor. It has a limited number of candidates to check, and once they're gone, the project is over. A new Fermat Prime Divisor earns the finder a rare badge. The project has found 18 primes so far, but no divisor.
For more information and discussion, read this forum thread or join our Discord server.

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