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-   Twin Prime Search (https://www.mersenneforum.org/forumdisplay.php?f=65)

 lsoule 2006-06-13 21:24

268964355*2^195000-1 is prime! Time : 90.980 sec.
269367765*2^195000-1 is prime! Time : 100.803 sec.

 Citrix 2006-06-14 02:59

196134045*2^195000+1 is prime!

My first prime for this project.:banana:

 victor 2006-06-14 06:33

Do you mean 196134045*2^195000-1 is prime too???

 Citrix 2006-06-14 07:49

No the -1 is not prime

 victor 2006-06-14 13:55

Ok :)
And why do you check for +1 first?

 pacionet 2006-06-14 14:45

What is the actual ratio PRIMES / MILLIONS TESTED ?

 Citrix 2006-06-14 15:52

[QUOTE=victor]Ok :)
And why do you check for +1 first?[/QUOTE]

Does it make any difference, which I check first.

 victor 2006-06-14 16:07

[QUOTE=Citrix]Does it make any difference, which I check first.[/QUOTE]
Not at all, in fact I don't care. It was only for information.

 Citrix 2006-06-14 16:54

I have an LLRnet server set up for +1 numbers, so I prefer working on +1 numbers. If I wanted to do -1 search, I will have to modify all my computers, which will be a hassle. Hence, I tested +1 primes.

 pacionet 2006-06-15 07:10

Ok I computed actual ratio: it should be 47 primes on 255 Millions tested, that is

0.184313

It means we are finding a prime every 5.42 Millions.

We are slightly under previsions (between 0.2 and 0.25) .

 biwema 2006-06-15 09:43

Where The number of twins remains constant (After sieving to 83T, a range of 24.7G and 10005865 Candidates it is one twin every 13.77G), the average Gap between Primes is increasing proportiona to the ratio of the log(sieving limit).
That means sieving to 45 bit instead if 44 bit means a 45/44 larger gap between the primes. (Reason: The sieve is biased to finding twins)

The current value at 83T is a prime every 5.83M.

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