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Old 2005-03-06, 07:00   #2
geoff's Avatar
Mar 2003
New Zealand

115710 Posts
Default Getting started

Here is a rough guide using NewPGen to sieve and PRP to test. These programs are available for Windows and Linux and work pretty much the same way in both.

Choose a candidate k value to test from the Sierpinski or Riesel reservations threads by posting a message there. For this example I will choose k=2822 from the Sierpinski thread. (If you don't have any special preference then choose one from the Sierpinski thread). For the Sierpinski k we need to find a prime of the form k*5^n+1, and for the Riesel k we need one of the form k*5^n-1. Any prime will do.

Note the value in the 'min. n untested' column for your k, in this case nmin=54000.

Sieving. Decide the largest value of n you are prepared to test for this candidate, call it nmax. If this is your first time then you will have to guess, but for this example nmax=200000 would be reasonable I think. Start newpgen and select these options from the menu:

create a new file: yes
output file name: 2822.out (this can be anything you like)
base: 5
sieve type: k*b^n+1 with k fixed (type 16)
k: 2822
nmin: 54000
nmax: 200000

For a Riesel candidate the only difference is the sieve type, use k*b^n-1 with k fixed (type 17) instead.

Start sieving. How long to sieve? I am still learning by trial and error, but in any case it is never worth continuing to sieve once the rate at which candidates are being removed is greater than the time it takes to PRP test the largest candidate, and it is probably worth stopping well before that point. Of course you don't know how long a PRP test takes until you try it :-).

Stop sieving. The output file will contain a list of candidates for PRP testing.

Start prp (or prp3 for SSE2 capable machines), in Linux use the -m command line option. Choose the 'Input data' menu item and enter the name of the newpgen file as the input file, choose a file name (e.g. prp.out) for the output file, and set the line number to 1.

Start prp testing. If a probable prime is found it will say so in the results.txt file and on screen, and a line will be written to the prp.out file. You can either do a primality test yourself using software like pfgw or proth.exe, or you can just report the probable prime and someone else will check it.

If you don't find a probable prime, then report how far you tested (the n value) so the next person doesn't repeat any work.

If you want to continue sieving deeper after prp testing part of the file, just remove the lines that were tested with a text editor and then use the 'continue sieving an old file' option in NewPGen. When starting prp testing again, go into the input data menu and reset the line number to 1. (or delete the prp.ini and start again).

If anyone else has links to other software, then please post them here, I will try to write up a proper introduction message eventually. Also if anyone has advice on how to choose how far to sieve that would be useful.

Good luck. Any problems, just post here.

Last fiddled with by geoff on 2005-03-06 at 07:09
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