mersenneforum.org  

Go Back   mersenneforum.org > Great Internet Mersenne Prime Search > Software

Reply
 
Thread Tools
Old 2021-06-28, 02:06   #320
Chuck
 
Chuck's Avatar
 
May 2011
Orange Park, FL

5×179 Posts
Default

Quote:
Originally Posted by ATH View Post
I guess this could not be an mprime issue? Just in case could someone with a Prime95 (Windows) AVX-512 computer test one of these? No need to finish it unless you want to, just run like 50% of stage1 to check if you get a roundoff error:
Pplus1=N/A,1,2,4037479,-1,2500000,250000000,2,70
Pplus1=N/A,1,2,4040059,-1,2500000,250000000,2,70
I'll try these two.
Chuck is offline   Reply With Quote
Old 2021-06-28, 02:32   #321
Chuck
 
Chuck's Avatar
 
May 2011
Orange Park, FL

11011111112 Posts
Default

I didn't get any roundoff errors.
Attached Thumbnails
Click image for larger version

Name:	test1.jpg
Views:	48
Size:	180.2 KB
ID:	25200   Click image for larger version

Name:	test2.jpg
Views:	45
Size:	177.7 KB
ID:	25201  
Chuck is offline   Reply With Quote
Old 2021-06-28, 04:21   #322
Citrix
 
Citrix's Avatar
 
Jun 2003

2·7·113 Posts
Default

If doing P-1 work on (k^p-1)/(k-1) or (k^p+1)/(k+1) with p prime
Does Prime95 automatically includes p in the B1 stage?


Thanks
Citrix is offline   Reply With Quote
Old 2021-06-28, 05:47   #323
ATH
Einyen
 
ATH's Avatar
 
Dec 2003
Denmark

23·397 Posts
Default

Quote:
Originally Posted by Chuck View Post
I didn't get any roundoff errors.
@Prime95: Is this strange that there are no roundoff errors in Prime95 on AVX-512 200K on these 2 exponents that I got roundoff errors on in mprime? or is it very dependent on the specific processor?

Last fiddled with by ATH on 2021-06-28 at 05:47
ATH is offline   Reply With Quote
Old 2021-06-28, 07:18   #324
Prime95
P90 years forever!
 
Prime95's Avatar
 
Aug 2002
Yeehaw, FL

167258 Posts
Default

Quote:
Originally Posted by Citrix View Post
If doing P-1 work on (k^p-1)/(k-1) or (k^p+1)/(k+1) with p prime
Does Prime95 automatically includes p in the B1 stage?
I believe so. Can you run a small test case?
Prime95 is offline   Reply With Quote
Old 2021-06-28, 07:19   #325
Prime95
P90 years forever!
 
Prime95's Avatar
 
Aug 2002
Yeehaw, FL

7×1,091 Posts
Default

Quote:
Originally Posted by ATH View Post
@Prime95: Is this strange that there are no roundoff errors in Prime95 on AVX-512 200K on these 2 exponents that I got roundoff errors on in mprime? or is it very dependent on the specific processor?
One started at 2/7, the other started at 6/5.
Prime95 is offline   Reply With Quote
Old 2021-06-28, 17:37   #326
ATH
Einyen
 
ATH's Avatar
 
Dec 2003
Denmark

61508 Posts
Default

Quote:
Originally Posted by Prime95 View Post
One started at 2/7, the other started at 6/5.
Yeah I switched it :( In case whoever tested it wanted to finish it, then it would not be wasted effort.


Quote:
Originally Posted by Prime95 View Post
Other AVX-512 FFT maximum exponents that remain to be tested (turn on roundoff checking):

Code:
22469
33423
I'm working on these 2 and going upwards after them. I'm doing P+1, do I need to do P-1 as well on each exponent?
Should I continue above the maximum in case of no failures below?

Edit: I reached a failure in the 33423 case. I started at M32611 and reached a roundoff error at M33391, should I do more testing for this FFT?

Code:
[Work thread Jun 28 16:01:03] P+1 on M33391, start=2/7, B1=100000000, B2=10000000000
[Work thread Jun 28 16:01:03] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:09:30] Possible roundoff error (0.4520854), backtracking to last save file.
[Work thread Jun 28 16:09:30] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:17:55] Possible roundoff error (0.4520854), backtracking to last save file.
[Work thread Jun 28 16:17:55] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:26:17] Possible roundoff error (0.4520854), backtracking to last save file.
Max roundoff errors before the failure:
M33301 Round off: 0.4065263058
M33347 Round off: 0.4113334932
M33353 Round off: 0.4064540519
M33359 Round off: 0.401012083
M33377 Round off: 0.4146345477

Last fiddled with by ATH on 2021-06-28 at 18:06
ATH is offline   Reply With Quote
Old 2021-06-28, 19:49   #327
R. Gerbicz
 
R. Gerbicz's Avatar
 
"Robert Gerbicz"
Oct 2005
Hungary

149410 Posts
Default

Quote:
Originally Posted by ATH View Post
Yeah I switched it :( In case whoever tested it wanted to finish it, then it would not be wasted effort.
...
I'm doing P+1, do I need to do P-1 as well on each exponent?
Should I continue above the maximum in case of no failures below?

Edit: I reached a failure in the 33423 case. I started at M32611 and reached a roundoff error at M33391, should I do more testing for this FFT?

Code:
[Work thread Jun 28 16:01:03] P+1 on M33391, start=2/7, B1=100000000, B2=10000000000
[Work thread Jun 28 16:01:03] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:09:30] Possible roundoff error (0.4520854), backtracking to last save file.
[Work thread Jun 28 16:09:30] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:17:55] Possible roundoff error (0.4520854), backtracking to last save file.
[Work thread Jun 28 16:17:55] Using AVX-512 FFT length 1536
[Work thread Jun 28 16:26:17] Possible roundoff error (0.4520854), backtracking to last save file.
Max roundoff errors before the failure:
M33301 Round off: 0.4065263058
M33347 Round off: 0.4113334932
M33353 Round off: 0.4064540519
M33359 Round off: 0.401012083
M33377 Round off: 0.4146345477
For example on M33391 we know a pretty large d (=p1*p2*p3*p4) divisor which enables a good error checking at least on the first stage of P+-1 : do the computation also in Z[d] and then regularly do the check for the intermediate number(s) that r(i) mod d is still good. What could give you a greedy FFT size.

Or for example at P-1 test the check is only: we computed that b^e==res mod N then check: res==b^(e mod eulerphi(d)) mod d [Euler-Fermat], for gcd(b,d)=1 and d|N, so you need to update only the e mod eulerphi(d) at each step and not the slightly more costly b^e mod d. [since d is usually very small compared to N this makes not a large difference in timing].

Last fiddled with by R. Gerbicz on 2021-06-28 at 19:52 Reason: typo, corrections
R. Gerbicz is offline   Reply With Quote
Old 2021-06-28, 20:13   #328
Prime95
P90 years forever!
 
Prime95's Avatar
 
Aug 2002
Yeehaw, FL

7·1,091 Posts
Default

Quote:
Originally Posted by ATH View Post
I'm doing P+1, do I need to do P-1 as well on each exponent?
Should I continue above the maximum in case of no failures below?
P+1 is sufficient. Don't go above the maximum if no failures are found.

Quote:
I started at M32611 and reached a roundoff error at M33391, should I do more testing for this FFT?
To be safe, length 1.5K AVX-512 FFT max exponent changed to 33380.
Prime95 is offline   Reply With Quote
Old 2021-07-14, 23:46   #329
Viliam Furik
 
Viliam Furik's Avatar
 
"Viliam Furík"
Jul 2018
Martin, Slovakia

2·11·31 Posts
Default

I am having a worker-count related issue with Prime95. I have been using (4 workers, 3 cores) configuration for a while. Now I've decided to make it (12 workers, 1 core), because of the better throughput at 50K FFT, which is what I am doing now - P-1 in 1M range on factored exponents. So I went and set the Prime95 accordingly. When I started the workers, it went fine, but when it got to starting worker #6, it crashed. The same happened when I restarted the program.

Workers #1 to #4 have plenty of work in their worktodo entries, worker #5 was assigned CERT, but the rest is hungry. Is it possible that it crashes because of that?

I am using version 30.6b4, processor is Ryzen 9 3900X (12 cores).

After a few testing attempts, it seems to crash precisely when all the first 4 workers finally agreed on RAM consumption (3 of them are in stage 2) and started working. That happens somewhere around the start of worker #8, i.e. about 40 seconds after the start of the program (there are 5-second delays between worker starts).
Viliam Furik is offline   Reply With Quote
Old 2021-07-15, 01:30   #330
Viliam Furik
 
Viliam Furik's Avatar
 
"Viliam Furík"
Jul 2018
Martin, Slovakia

2·11·31 Posts
Default

Weird... When I fed the workers with assignments, it's no longer crashing.

But I am going to (6 workers, 2 cores), because 12 workers make the CPU really hot, 92 °C.
Viliam Furik is offline   Reply With Quote
Reply

Thread Tools


All times are UTC. The time now is 10:29.


Sat Oct 23 10:29:02 UTC 2021 up 92 days, 4:58, 0 users, load averages: 1.40, 1.16, 1.17

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, 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.