mersenneforum.org Could something be wrong with Linux sr5sieve?
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 2007-03-10, 18:54 #1 jasong     "Jason Goatcher" Mar 2005 3×7×167 Posts Could something be wrong with Linux sr5sieve? 1315 factors found 5700-5750, expected 1440. That's a pretty extreme difference, in my opinion. What do you guys think?
 2007-03-10, 19:00 #2 masser     Jul 2003 wear a mask 1,609 Posts No, that's not too bad. I wouldn't be too worried.
2007-03-10, 23:53   #3
geoff

Mar 2003
New Zealand

13·89 Posts

Quote:
 Originally Posted by jasong 1315 factors found 5700-5750, expected 1440. That's a pretty extreme difference, in my opinion. What do you guys think?
Don't take the expected number of factors too seriously, the formula is not very accurate. It is calculated as N*(1-log(pmin)/log(pmax)) where N is the number of remaining terms, and pmin <= p <= pmax the range of factors tested.

Does anyone know a better estimate?

Last fiddled with by geoff on 2007-03-10 at 23:54 Reason: missing ')'

 2007-03-12, 03:13 #4 geoff     Mar 2003 New Zealand 100100001012 Posts I you are concerned that factors are being missed, there is a small test sieve sr5check.tar.gz at http://www.geocities.com/g_w_reynolds/sr5sieve/tests. There are instructions in the enclosed README, but briefly if you download sr5check.tar.gz and run sr5sieve -i sr5check.txt -p 100e6 -P 150e6' it should find 10533 new factors, and the factors.txt file should match the checked-factors.txt file (which has been verified with NewPGen 2.82). Another test in included in the sr5sieve source (see INSTALL): running make realclean' then `make ARCH=k8 check' will test the modular arithmetic functions against GMP (for the -k8 build in this case). You need to have libgmp installed for this test. Of course there are many corner cases that are not covered, but if both of these tests pass then that should give a reasonable assurance that most factors are being found in normal use.

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