20200223, 22:27  #463 
"Alexander"
Nov 2008
The Alamo City
3·131 Posts 
PFGW can do a deterministic (i.e. proven prime rather than probably prime) P+1 test on Riesel candidates by passing the tp argument to it. However, said algorithm is not as efficient as LLR, and I generally only use PFGW on Riesel candidates when the numbers are small (n < 10,000), where the cost of writing the LLR log to disk slows it down considerably versus PFGW (which only writes when a prime is found).

20200304, 22:27  #464 
"Erling B."
Dec 2005
7·11 Posts 
I also found a big speed difference llr in favor for thouse old cpu I am using. I stick to llr at the moment doing Riesel numbers. Thanks for all the help here.
Last fiddled with by japelprime on 20200304 at 22:32 
20200305, 00:08  #465 
Sep 2002
Database er0rr
3,449 Posts 
If there is a "big speed difference" then it is most likely to be due to the different FFT sizes used.
Last fiddled with by paulunderwood on 20200305 at 07:05 
20200305, 00:18  #466 
"Mark"
Apr 2003
Between here and the
13501_{8} Posts 
llr will be faster for most, if not all, numbers of the form k*b^n+/c because it uses a different algorithm. I have purposefully not changed pfgw to use a faster algorithm because it allows for one program to verify the results of the other.

20200704, 11:29  #467 
Feb 2019
1001010_{2} Posts 
Is it possible to automatically stop pfgw once a prp is found?
I read about setting number_primes in the input file, but it doesn't seem to work for me :/ Does number_primes only work with confirmed primes (ignoring prps)? 
20200704, 13:19  #468  
"Mark"
Apr 2003
Between here and the
5,953 Posts 
Quote:
So if you have multiple values for $a, it will continue searching. Post your input file and explain what you are trying to accomplish. 

20200704, 13:43  #469 
Dec 2011
After milion nines:)
2^{2}·337 Posts 

20200704, 14:45  #470  
Feb 2019
2×37 Posts 
Quote:
I may misinterpreted the function of {number_primes,$a,1}. I'd like to search for the smallest prp larger than some 10^n and I wish to stop the program once it found it, so it doesn't search the entire sieve file then. I attached a sieve file for n=4k with candidates of the form 10^4000+c, made with fkbnsieve. So when pfgw finds 10^4000+"something" is prp, I'd like it to stop and search no further. Last fiddled with by matzetoni on 20200704 at 14:46 

20200704, 15:34  #471  
"Mark"
Apr 2003
Between here and the
5953_{10} Posts 
Quote:
I think that you will need to use an edited to change to this format: Code:
ABCD $a^4000+$b [10 61] // {number_primes,$a,1} 0 +50 

20200704, 16:09  #472  
Feb 2019
1001010_{2} Posts 
Quote:
That works! Thanks a lot! 

20200715, 20:47  #473 
Sep 2010
Portland, OR
7×53 Posts 
Another repunit which fails with special modular reduction
I found another repunit which fails repeatedly when run with special modular reduction. This is using pfgw4.0.1, which uses square_carefully for the last 50 iterations. (See post https://www.mersenneforum.org/showpo...&postcount=415 for a previous case.)
In this case the offender is (10^45688991)/9: Code:
Detected in MAXERR>0.45 (round off check) in prp_using_gwnum Iteration: 15177501/15177550 ERROR: ROUND OFF 0.5>0.45 PFGW will automatically rerun the test with a1 ... Detected in MAXERR>0.45 (round off check) in prp_using_gwnum Iteration: 15177501/15177550 ERROR: ROUND OFF 0.5>0.45 PFGW will automatically rerun the test with a6 (10^45688991)/9 ERROR DURING PROCESSING! (96541.0526s+0.0304s) 
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