mersenneforum.org  

Go Back   mersenneforum.org > Prime Search Projects > Riesel Prime Search

Reply
 
Thread Tools
Old 2018-10-26, 04:11   #1
chunsonnn
 
Oct 2018

116 Posts
Default Does NewPGen have a bug?

I was sieving k=173 from n=1M to n=2M, and I found this message by NewPGen:

p=2215115304221 divides n=1798220.

However 2,215,115,304,221 is composite (that number is 8627 * 256765423), so that message should not have popped up. Why didn't NewPGen remove n=1798220 when it was at p=8627 or at p=256765423?

In case anyone's wondering, I was using NewPGen version 2.82 on a Pentium 4 computer. The problem also appears on another Pentium 4 machine, so I'm pretty sure it's not a hardware problem.

Thank
Cristiano
chunsonnn is offline   Reply With Quote
Old 2018-10-26, 04:31   #2
axn
 
axn's Avatar
 
Jun 2003

17×263 Posts
Default

Quote:
Originally Posted by chunsonnn View Post
I was sieving k=173 from n=1M to n=2M, and I found this message by NewPGen:

p=2215115304221 divides n=1798220.

However 2,215,115,304,221 is composite (that number is 8627 * 256765423), so that message should not have popped up. Why didn't NewPGen remove n=1798220 when it was at p=8627 or at p=256765423?

In case anyone's wondering, I was using NewPGen version 2.82 on a Pentium 4 computer. The problem also appears on another Pentium 4 machine, so I'm pretty sure it's not a hardware problem.

Thank
Cristiano
p=2215115304211 divides 173*2^1798220-1
axn is offline   Reply With Quote
Old 2018-10-26, 06:28   #3
paulunderwood
 
paulunderwood's Avatar
 
Sep 2002
Database er0rr

3·1,033 Posts
Default

Isn't k=173 already sieved very deeply by PrimeGrid?
paulunderwood is online now   Reply With Quote
Old 2018-10-26, 12:01   #4
ATH
Einyen
 
ATH's Avatar
 
Dec 2003
Denmark

3×13×71 Posts
Default

Neither 8627 nor 256765423 is a factor of 173*2^1798220-1, so it must have been p=2215115304211 as axn pointed out.
ATH is offline   Reply With Quote
Old 2018-10-26, 12:08   #5
pinhodecarlos
 
pinhodecarlos's Avatar
 
"Carlos Pinho"
Oct 2011
Milton Keynes, UK

112·37 Posts
Default

Quote:
Originally Posted by paulunderwood View Post
Isn't k=173 already sieved very deeply by PrimeGrid?
Yes and tested up to n=2.04M by RPS.
pinhodecarlos is offline   Reply With Quote
Old 2018-10-26, 13:26   #6
rogue
 
rogue's Avatar
 
"Mark"
Apr 2003
Between here and the

11×509 Posts
Default

Why are you using newpgen for this form? Use srsieve/sr1sieve. They are much, much faster than newpgen for this form.
rogue is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
NewPgen Cybertronic Factoring 0 2014-03-22 10:07
Does NewPGen have a bug? MooooMoo Riesel Prime Search 16 2008-12-11 11:46
NewPGen k value problem roger Information & Answers 0 2007-04-04 22:38
NewPGen reliability Cruelty Riesel Prime Search 3 2006-02-15 05:15
Problem with Newpgen Zenmastur Software 4 2003-08-02 19:43

All times are UTC. The time now is 22:41.

Wed Feb 19 22:41:40 UTC 2020 up 19 days, 17:13, 2 users, load averages: 1.96, 2.15, 2.27

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.