20210613, 13:11  #309 
"David Kirkby"
Jan 2021
Althorne, Essex, UK
3·149 Posts 
Oops. Given you say it's completed, there's probably no harm in having the AID printed, as it would be expired now. At least I think that's the case  I would still not print it myself, just in case, but I think you are safe the fact it has completed.

20210613, 13:17  #310  
"Viliam Furík"
Jul 2018
Martin, Slovakia
2A8_{16} Posts 
Quote:
The fact, that the factor has 31 bits (rounded up) suggests it's true because 11115983  31 = 11115952. Last fiddled with by masser on 20210613 at 22:35 

20210613, 14:01  #311  
Sep 2008
Kansas
2^{3}·431 Posts 
Quote:
Code:
[Work thread Jun 13 03:17] Iteration: 5800000 / 6397693 [90.65%], ms/iter: 1.524, ETA: 00:15:10 Code:
PRPDC=5F.....9D,1,2,6397693,1,99,0,3,5,"1880921743,150224692370214966223" 

20210615, 10:23  #312 
"Alexander"
Nov 2008
The Alamo City
1011110110_{2} Posts 
Well, of course there's that. I should have said there was no special binary form, beyond a couple of bits (guaranteed by the 2kp+1 form). Recall, a Mersenne number is all 1's in binary.
Last fiddled with by Happy5214 on 20210615 at 10:25 
20210615, 12:08  #313 
"Viliam Furík"
Jul 2018
Martin, Slovakia
2^{3}·5·17 Posts 
Yes, of course. I just wanted to point out the tiny error that made the statement false. Otherwise, I agree.

20210624, 19:20  #314 
Einyen
Dec 2003
Denmark
5^{2}·127 Posts 
Weird single exponent FFT issue: I'm doing P+1 in the 4M range in mprime 30.6b4 and at the exponent M4037479 kept failing with the chosen AVX512 FFT 200K.
Pplus1=N/A,1,2,4037479,1,2500000,250000000,1,70 It did not work until I added ExtraSafetymargin=0.03 to prime.txt forcing it to use 240K FFT. But subsequent exponents works fine at AVX512 FFT 200K, and that exponent M4037479 also works fine with FMA3 FFT 200K (in Prime95 30.6b4). Code:
[Work thread Jun 20 12:38:29] P+1 on M4037479, start=2/7, B1=2500000, B2=TBD [Work thread Jun 20 12:38:29] Using AVX512 FFT length 200K, Pass1=640, Pass2=320, clm=1 [Work thread Jun 20 12:42:20] Possible roundoff error (0.44758343), backtracking to last save file. [Work thread Jun 20 12:42:20] Using AVX512 FFT length 200K, Pass1=640, Pass2=320, clm=1 [Work thread Jun 20 12:46:12] Possible roundoff error (0.44758343), backtracking to last save file. [Work thread Jun 20 12:46:12] Using AVX512 FFT length 200K, Pass1=640, Pass2=320, clm=1 [Work thread Jun 20 12:50:12] Possible roundoff error (0.44758343), backtracking to last save file. Last fiddled with by ATH on 20210624 at 19:22 
20210624, 20:08  #315 
P90 years forever!
Aug 2002
Yeehaw, FL
2^{4}·3^{2}·53 Posts 
That happened to me too a week ago. I changed the code (in 30.7) so that if an error occurs it retries with a maximum allowable error of 0.46. I suppose it could still infinite loop if an even worse roundoff error is encountered.
Last fiddled with by Prime95 on 20210624 at 20:10 
20210625, 19:41  #316 
Einyen
Dec 2003
Denmark
6147_{8} Posts 
Happened again and only for 200K AVX512, worked fine on 200K FMA3. I will leave ExtraSafetymargin=0.03 on for now and use 240K AVX512.
Code:
[Work thread Jun 24 22:19:42] P+1 on M4040059, start=2/7, B1=2500000, B2=TBD [Work thread Jun 24 23:52:22] Possible roundoff error (0.43976434), backtracking to last save file. [Work thread Jun 24 23:52:22] Using AVX512 FFT length 200K, Pass1=640, Pass2=320, clm=1 [Work thread Jun 24 23:52:22] M4040059 stage 1 is 70.105240% complete. [Work thread Jun 24 23:59:19] Possible roundoff error (0.43976434), backtracking to last save file. [Work thread Jun 24 23:59:19] Using AVX512 FFT length 200K, Pass1=640, Pass2=320, clm=1 [Work thread Jun 24 23:59:19] M4040059 stage 1 is 70.105240% complete. [Work thread Jun 25 00:06:16] Possible roundoff error (0.43976434), backtracking to last save file. 
20210627, 09:04  #317 
P90 years forever!
Aug 2002
Yeehaw, FL
2^{4}·3^{2}·53 Posts 

20210627, 15:50  #318  
Einyen
Dec 2003
Denmark
5^{2}×127 Posts 
Quote:
It could be hard to find though, since not all exponents above a certain threshold gives the error. I turned back to AVX512 200K FFT for a while before I got the 2nd error, and these 7 exponents worked fine at 200K: M4039429,M4039447,M4039487,M4039537,M4039583,M4039733,M4039843 I guess this could not be an mprime issue? Just in case could someone with a Prime95 (Windows) AVX512 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 Last fiddled with by ATH on 20210627 at 16:10 

20210627, 17:19  #319  
P90 years forever!
Aug 2002
Yeehaw, FL
7632_{10} Posts 
Quote:
Other AVX512 FFT maximum exponents that remain to be tested (turn on roundoff checking): Code:
22469 33423 44307 98407 108700 130200 151300 162400 172600 194300 214800 225600 256500 267400 382900 424300 507400 527800 672200 835300 1001000 1161000 1244000 1324000 1490000 1649000 1730000 1976000 2457000 2616000 2941000 3893000 4843000 5623000 5798000 6022000 6408000 6730000 7219000 7682000 7815000 7985000 8384000 8640000 8907000 9547000 10020000 
