Join PrimeGrid
Returning Participants
Community
Leader Boards
Results
Other
drummerslowrise

1)
Message boards :
General discussion :
Favourite Prime Number.
(Message 118541)
Posted 433 days ago by serge
My favorite number is the 26th EisensteinMersenne Norm prime: 3^2237561+3^1118781+1
My second favorite is the prime partitions number of a number which is square: partitions(14881^2)

2)
Message boards :
General discussion :
A new Mersenne prime was found (50th known)
(Message 112732)
Posted 597 days ago by serge
See http://mersenneforum.org/showthread.php?t=22837
A day after Christmas a computer has reported a new Mersenne prime.
...finished (first) doublecheck:
Mxxxxxxxx is prime!
Congratulations to all GIMPS participants on their 20+ years of continuing team effort!

3)
Message boards :
News :
GFN1048576 Mega Prime!
(Message 109845)
Posted 714 days ago by serge
Extends https://oeis.org/A056993 (posted).
Congratulations!

4)
Message boards :
Generalized Cullen/Woodall prime search :
GCWLLR is now open!
(Message 108874)
Posted 770 days ago by serge
With GCW now above 2 million digits, when will the next prime be found?
At this size and assuming ~4550bit prefactoring, 1 in ~150,000 tests may find a prime.
(Of course, once 150,000 tests will be done, the size will increase, and the goal posts will move further...)
How many units are processed per week on average? Divide one by the other and you will have the answer (+90% CI).

5)
Message boards :
Generalized Cullen/Woodall prime search :
How to speed up (some) GCW units by 10%+
(Message 107909)
Posted 825 days ago by serge
Maybe LLR's philosophy is "the client is always right!"
I.e.: If the input file calls for a test of a specific FFT or a "specific arrangement of bits", then that's what it will run (even if slower, because "this is the test that was ordered").
But it indeed doesn't follow this rule for powers of 2.
bash4.2$ llr d q"27*1024^10007+1"
Starting Proth prime test of 27*2^100070+1
Using allcomplex FMA3 FFT length 10K, Pass1=128, Pass2=80, a = 11
27*2^100070+1 is not prime. Proth RES64: C14E6737D2E78E5E Time : 5.261 sec.
bash4.2$ llr d q"28*729^10007+1"
Base prime factor(s) taken : 3
Starting N1 prime test of 28*729^10007+1
Using allcomplex FMA3 FFT length 10K, Pass1=128, Pass2=80, a = 3
28*729^10007+1 is not prime. RES64: E83080E955E9B281. OLD64: B89182BC01BD1780 Time : 4.888 sec.
bash4.2$ llr d q"28*10000^10007+1"
Base factorized as : 2^4*5^4
Base prime factor(s) taken : 5
Starting N1 prime test of 28*10000^10007+1
Using allcomplex FMA3 FFT length 18K, Pass1=384, Pass2=48, a = 3
28*10000^10007+1 is not prime. RES64: 59CCA66A39ED54C4. OLD64: 0D65F33EADC7FE48 Time : 13.645 sec.
(and of course it is fully equipped to normalize the base, as a side effect of factoring the base for the purposes of the N1 mechanics.)
PFGW does what it is ordered by the input file, too.

6)
Message boards :
Generalized Cullen/Woodall prime search :
How to speed up (some) GCW units by 10%+
(Message 107890)
Posted 826 days ago by serge
It seems that in your clientserver set up the ideal place to put the reformatter would be the primegrid_llr_wrapper. It would keep the initial task parameters, reformat for (c)llr, get the result back from (c)llr, report back to server as initially requested. Then the database, the server and the accounting code would be unchanged.
primegrid_llr_wrapper for now can do only:
▪ square simplification,
▪ k simplification
Later, it can be extended to recognize b being any power. See here 
Curiously, these numbers may be hard to recognize when written in standard form (emphasis mine).
For example, they may be like
18740*3^1686621
which could be written
168660*3^1686601.
More difficult to spot are those like the following:
9750*7^292501 = 9750*7^(3*9750)1 = 9750*343^97501
8511*2^3744861 = (8511*2^2)*2^(11*8511)*41 = 34044*2048^340441.
This is in fact how the GCWs for 25, 49, 121 will end up showing in UTM lists. (And this is how GW for b=4 looks, indeed.)

7)
Message boards :
Generalized Cullen/Woodall prime search :
How to speed up (some) GCW units by 10%+
(Message 107876)
Posted 827 days ago by serge
For LLR it is not the number that matters, but the (k,b,n,c) form, and b is taken by it verbatim, as given.
I am not ready to go into a very deep explanation, but I will try to make an approximation to an explanation (not meant to be taken for that this is exact). With b=11, it is possible to form an array of length 640K where each element is a quasidigit ("limb") in an unusual representation: some digit's weights are perhaps 11^6 and some digit's weights are 11^7, or something like that. (Off the top of my head, what I remember is that each limb on average is limited to keeping ~30 bits of information, or something like that.) Only powers of b can be used as limb weights.
In contrast if the number is entered with b=121, the program can only work with limbs of, say, 121^3 and 121^2. (It has less opportunities to pack, the larger the b.) For that reason it ponders the array of length 640K and thinks, "nah, some elements will be too large; gotta go for next FFT size", and so it does.
Long story short, using the simplest possible (k,b,n,c) (with b as low as possible) will lend more possibilities for more dense FFT arrays. If not only b=121, but also k is divisible by 11, the FFT size may be even smaller if (k,121,n,c) is transformed into (k/11,11,2*n+1,c).
As an aside, yes, it would be nice if LLR did it all itself, but as the timing test (shown earlier) demonstrates  it doesn't. But here's where we can help LLR and do transformation externally, serverside. The transformation logic is quite straightforward.[/i]

8)
Message boards :
Generalized Cullen/Woodall prime search :
How to speed up (some) GCW units by 10%+
(Message 107873)
Posted 827 days ago by serge
Nothing of what I am about to write is new. Or difficult.
And it has already been discussed multiple times.
Observe that some the chosen bases for this particular subproject happen to be squares.
25 = 5^2, 49 = 7^2, 121 = 11^2. Some people even know that this was a deliberate choice. I've been waiting for a workunit to arrive for one of these bases for a while, and now I have one.
The candidate is 754806*121^754806+1 which can also be easily regrouped as 754806*11^1509612+1.
Let's compare:
/home/serge/NumTheory/GCW> llr d d.npg
Base prime factor(s) taken : 11
Starting N1 prime test of 754806*121^754806+1
Using zeropadded AVX FFT length 720K, Pass1=320, Pass2=2304, a = 3
754806*121^754806+1, bit: 70000 / 5222413 [1.34%]. Time per bit: 5.654 ms.
/home/serge/NumTheory/GCW/2> llr d d2.npg
Base prime factor(s) taken : 11
Starting N1 prime test of 754806*11^1509612+1
Using zeropadded AVX FFT length 640K, Pass1=640, Pass2=1K, a = 3
754806*11^1509612+1, bit: 40000 / 5222416 [0.76%]. Time per bit: 4.698 ms.
That's 20% faster. (Results are similar for AVX2.)
Why is the server sending this workunit task as 754806*121^754806+1 ?
Isn't it trivial, serverside, to fetch the candidate from the database and if/when b=x^2, send it to the client not as
100000000000000:P:1:b:1
n n
but as
100000000000000:P:1:x:1
n 2n
In this particular case:
100000000000000:P:1:11:1
754806 1509612
Too hard to implement?

9)
Message boards :
News :
World Record Generalized Woodall Prime
(Message 107778)
Posted 830 days ago by serge
Glad to see the announcement from John, and such early results from the project. Great work everyone!
Yes, sometimes the first news post here is old news. Hopefully people do not misunderstand this for a 2017 world record GW prime. /JeppeSN
There isn't though. Is there?
For all I see, there is a 2015 World Record Generalized Woodall Prime, and it belongs to ...hmmm... look at that, who could have guessed?
Of course not for long now, but still.

10)
Message boards :
General discussion :
Your Erdos Number
(Message 101671)
Posted 987 days ago by serge
Mine is 3.
Batalov > Lander > Kleitman > Erdos

Next 10 posts
