Finding Wrong Factors - Page 2

ATH · 2010-05-30, 15:15

64bit Prime95 25.11.2 finds the correct factors on Windows XP 64bit.

lindee · 2010-05-30, 22:42

Quote:

Originally Posted by __HRB__

What happens if you boot using a 64-bit live-CD from a different distro, run mprime (should have no errors), chroot, and run mprime again?

Using the previous Ubuntu 9.10 disc, I mounted the local partition and tested one of the exponents; mprime returned the correct factor. When I chroot and run it again, mprime returns the incorrect factor.

__HRB__ · 2010-05-30, 22:51

Quote:

Originally Posted by lindee

Using the previous Ubuntu 9.10 disc, I mounted the local partition and tested one of the exponents; mprime returned the correct factor. When I chroot and run it again, mprime returns the incorrect factor.

Quote:

Originally Posted by __HRB__

My bottom dollar is on a bug in a shared library in the (or your) Ubuntu installation/configuration.

Maybe I should leverage my bottom dollar. :-)

lindee · 2010-05-30, 23:58

Just created a virtual machine (on different hardware) and did a fresh install of Ubuntu 10.04 64-bit. The problem exists here as well.

henryzz · 2010-05-31, 10:56

Quote:

Originally Posted by lindee

Just created a virtual machine (on different hardware) and did a fresh install of Ubuntu 10.04 64-bit. The problem exists here as well.

Could you do a similar test with 9.10 or earlier(earlier than 8.04 would be a bit early)?

lindee · 2010-06-01, 16:38

I performed the same test on the VM as suggested by _HRB_ and the results were the same as the original problem PC. Booting into Ubuntu 9.10 and running mprime found the correct factor. Doing a chroot to the Ubuntu 10.04 installation resulted in mprime returning the wrong factor.

I am currently downloading the 32-bit version of Ubuntu 10.04 to see whether or not this bug is limited to just the 64-bit version.

henryzz · 2010-06-01, 16:48

Quote:

Originally Posted by lindee

I performed the same test on the VM as suggested by _HRB_ and the results were the same as the original problem PC. Booting into Ubuntu 9.10 and running mprime found the correct factor. Doing a chroot to the Ubuntu 10.04 installation resulted in mprime returning the wrong factor.

I am currently downloading the 32-bit version of Ubuntu 10.04 to see whether or not this bug is limited to just the 64-bit version.

sorry i didn't notice you had tried 9.10
comes of being away for a couple of weeks

lindee · 2010-06-01, 17:17

On the 32-bit Ubuntu 10.04, mprime found the correct factor.

ckdo · 2010-06-02, 15:45

Quote:

Originally Posted by lindee

One of my machines seems to have been reporting invalid factors for several exponents for about the past week.

[...]

Problem machine is Core2Quad running mprime 25.11 64-bit on Ubuntu 10.04. I think the problem started last Friday either during or after upgrading Ubuntu.

Has anyone else seen anything like this?

Addition: There is a pattern with the invalid factors. In the last seven digits of each invalid factor, the last three digits are always the same and the first three are always the same.

Same problem here. Q6600, Ubuntu Lucid x64, mprime 25.11 x64.

83 exponents affected over the last 43 days. Range=90-91M, depth=64-65 bits.

Will rerun those expos under Windoze as resources permit.

Cheers,

Carsten

fivemack · 2010-06-02, 15:55

No need to rerun them; the first sixteen-or-so digits are right and you know the value has to be 1 mod p, so a very quick search around the wrong answer will give the right one. Post exponents and wrong factors here and I will post correct factors

Prime95 · 2010-06-02, 23:26

Any volunteers to debug this? Look in the gtoc routine in gwnum/giants.c

2010-06-02, 15:55	#21
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 1917₁₆ Posts	No need to rerun them; the first sixteen-or-so digits are right and you know the value has to be 1 mod p, so a very quick search around the wrong answer will give the right one. Post exponents and wrong factors here and I will post correct factors Last fiddled with by fivemack on 2010-06-02 at 15:55

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2010-05-30, 15:15	#12
ATH Einyen Dec 2003 Denmark 2×1,579 Posts	64bit Prime95 25.11.2 finds the correct factors on Windows XP 64bit.

2010-05-30, 23:58	#15
lindee Feb 2009 3·11 Posts	Just created a virtual machine (on different hardware) and did a fresh install of Ubuntu 10.04 64-bit. The problem exists here as well.

2010-06-01, 16:38	#17
lindee Feb 2009 3×11 Posts	I performed the same test on the VM as suggested by _HRB_ and the results were the same as the original problem PC. Booting into Ubuntu 9.10 and running mprime found the correct factor. Doing a chroot to the Ubuntu 10.04 installation resulted in mprime returning the wrong factor. I am currently downloading the 32-bit version of Ubuntu 10.04 to see whether or not this bug is limited to just the 64-bit version.

2010-06-01, 17:17	#19
lindee Feb 2009 21₁₆ Posts	On the 32-bit Ubuntu 10.04, mprime found the correct factor.

2010-06-02, 23:26	#22
Prime95 P90 years forever! Aug 2002 Yeehaw, FL 7,537 Posts	Any volunteers to debug this? Look in the gtoc routine in gwnum/giants.c