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Old 2017-11-10, 22:35   #1
emiller
 
Apr 2017

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Default Endlessly Running Jacobi error check on v29.3

Ever since I upgraded to mprime v29.3, the program constantly loops through running Jacobi error check.

I managed to get mprime to perform my desired LL-type calculations for a short while, but eventually it reverts to this and remains stuck in this loop, constantly pushing out the expected completion date.


Is this a known bug?
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Old 2017-11-10, 22:55   #2
GP2
 
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Quote:
Originally Posted by emiller View Post
Ever since I upgraded to mprime v29.3, the program constantly loops through running Jacobi error check.
It could be a bug in the Jacobi error check code, but it seems more likely that your machine is producing errors and the Jacobi code is working as intended.

Has this machine worked on other exponents, and have any of them been double-checked yet?
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Old 2017-11-10, 22:57   #3
emiller
 
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It's actually occurring on two machines. Both have completed a number of now verified LL runs and both were running fine on v28 (can't remember the sub-version).
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Old 2017-11-10, 23:15   #4
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Quote:
Originally Posted by emiller View Post
It's actually occurring on two machines. Both have completed a number of now verified LL runs and both were running fine on v28 (can't remember the sub-version).
Maybe run some torture tests from the menu, to rule out the possibility of your machines having developed a problem recently. It seems unlikely that two machines would do so simultaneously, but perhaps they are plugged into the same wall outlet and power has been glitchy lately?

Can you give some examples of output from the results.txt or prime.log files?

Are you willing to share what the exponents are? They might be close to an FFT size boundary. I could try running a double check or triple check to see if the problem is reproducible.
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Old 2017-11-10, 23:19   #5
Prime95
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Can you post the screen output (or email me)? Perhaps there is a bug in recovering from a failed Jacobi check.

In the meantime you can put "JacobiErrorCheck=0" in prime.txt.
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Old 2017-11-11, 00:18   #6
emiller
 
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Quote:
Originally Posted by Prime95 View Post
Can you post the screen output (or email me)? Perhaps there is a bug in recovering from a failed Jacobi check.

In the meantime you can put "JacobiErrorCheck=0" in prime.txt.
I sent you a private message via this forum's interface.

Looking through my prime.log file, it seems my previous version was v28.10.


I had experienced this as soon as I updated to v29.3. I let things run for a while (days, maybe even weeks). It kept repeating the error check over and over again. I then decided to clear out some of my computer-specific files. This resulted in the checkout of new exponents, one for each machine, and I see now that after running for a few percent, things have returned to this endless check.
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Old 2017-11-11, 02:07   #7
Prime95
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Here is the key output from the log you sent me: "Passed. Time: 93923.444 sec."

This error check takes 30 seconds on my computer! Since these Jacobi checks are scheduled to run every 12 hours and your test takes over a day to complete, you will indeed have an infinite loop of Jacobi checks.

Can you look around for libgmp_10.dll on your machine and post the dates? My only guess right now is Windows is locating an older, slower version of libgmp. Others here may have other ideas as to what could cause this.
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Old 2017-11-11, 02:42   #8
emiller
 
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I think you hit the nail on the head, Prime95.

This is a CentOS6 machine and I did some unholy things to get around the missing libgmp.so.10.

I see what I did is mentioned in GP2's nice clear post here here.

And in that post, he astutely points out:

Quote:
Unfortunately,
yum whatprovides /usr/lib64/libgmp.so.3
indicates that this is gmp-4.3.1-12.el6.x86_64, and the fast Jacobi symbol code was introduced into GMP with version 5.0.0, which means the Jacobi code will run very slowly, maybe a hundred times slower.

So I probably should just bite the bullet and upgrade to centOS7.
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Old 2017-11-11, 04:28   #9
Prime95
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Get version 29.4. I've included the libgmp library in that release.
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Old 2017-11-11, 07:06   #10
GP2
 
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Huh... in my previous message it didn't occur to me that the old Jacobi library function could actually take longer than twelve hours.

In the Prime95 code, the call should be conditional:

[CODE]
# if __GNU_MP_VERSION >= 5
jacobi_error_check()
#endif
[/CODE]


Edit: hmm... that's a compile-time check obviously... according to the manual, there's also the global constant

Code:
const char * const gmp_version
which is a null-terminated string of the form, e.g., "5.0.0" (or just, e.g., "4.2" for very old versions).


The fast Jacobi function was introduced in GMP version 5.0.0 according to this old mailing list post.

Last fiddled with by GP2 on 2017-11-11 at 07:24
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Old 2017-11-14, 10:26   #11
GP2
 
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Quote:
Originally Posted by GP2 View Post
The fast Jacobi function was introduced in GMP version 5.0.0 according to this old mailing list post.
I misread the mailing list post that is linked above.

Version 5.0.0 still had the old (quadratic) code. It was actually GMP 5.1.0 that introduced the faster (subquadratic) code, see https://gmplib.org/gmp5.1.html or https://gmplib.org/list-archives/gmp...er/000036.html
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