20210506, 19:18  #1 
"David Kirkby"
Jan 2021
Althorne, Essex, UK
2·3·5·7 Posts 
How can one benchmark P1 testing?
I understand the latest version of mprime can use quite a bit or RAM for P1 testing. I have 384 GB, and wanted to know how much RAM to allocate on a dual CPU system. Each CPU has 192 GB local to it, so access that RAM faster than the other 192 GB. So I want wonder if its best to
1) Use most of the RAM  I have currently configured 320 GB 2) Use a bit less than half (say 180 GB), so that the RAM will be local to the one CPU. It's not so obvious to me how one would test what is best. Can one doublecheck a previous P1 test for timing purposes? I'm thinking it might be wise to try to check one that's known to have large factors, so are not easy to find. Dave Last fiddled with by drkirkby on 20210506 at 19:18 
20210506, 20:30  #2 
Apr 2010
Over the rainbow
2^{2}·641 Posts 
M27155813 has a 112.563bit (34digit) factor: 7669084564727955238545079945517857 (P1,B1=1350000,B2=109350000)
I have an i7 8700,3 core, 7 G of ram used at the time and it took me about 4H10 min Code:
[Mon Apr 5 18:22:15 2021] {"status":"NF", "exponent":27155767, "worktype":"P1", "b1":1350000, "b2":109350000, "fftlength":1474560, "securitycode":"B8093FA5", "program":{"name":"Prime95", "version":"30.4", "build":9, "port":4}, "timestamp":"20210405 16:22:15", "user":"firejuggler", "computer":"Maison", "aid":"FDC98300316E54D7F1FFCD2D72772124"} [Mon Apr 5 22:32:58 2021] {"status":"F", "exponent":27155813, "worktype":"P1", "factors":["7669084564727955238545079945517857"], "b1":1350000, "b2":109350000, "fftlength":1474560, "securitycode":"B8163FB2", "program":{"name":"Prime95", "version":"30.4", "build":9, "port":4}, "timestamp":"20210405 20:32:58", "user":"firejuggler", "computer":"Maison", "aid":"4F6AE55CF923BB50B3A542D7A37C3803"} 
20210506, 21:51  #3 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
3·29·59 Posts 
For exponents closer to the current wavefront, therefore quicker to test, try those in the middle of https://www.mersenneforum.org/showpo...51&postcount=3
For a list of P1 self test candidates with known factors, throughout the mersenne.org exponent range, see https://www.mersenneforum.org/showpo...8&postcount=31 Use the reference info instead of starting a new thread for everything! Last fiddled with by kriesel on 20210506 at 21:54 
20210506, 22:05  #4  
"Curtis"
Feb 2005
Riverside, CA
2·2,393 Posts 
Quote:
The forum generally likes having threads of reasonable questions with answers for future interested parties you could take advantage of this history and browse lots of threads that might match your interests. 

20210507, 08:54  #5  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
2×3×5×7 Posts 
Quote:
1) The new version of mprime is supposed to be much better for P1 factoring than older versions. That's why I upgraded yesterday. 2) Based on a P1 factoring I performed yesterday on M108399059 https://www.mersenne.org/report_expo...8399059&full=1 * GHz days = 21.7308 * B1=893 000, B2=51 571 000 That used significantly more GHz days than any previous attempt. The longest previous attempt was M110600107 https://www.mersenne.org/report_expo...0600107&full=1 * 13.2595 GHz days * B1=813 000, B2=24 770 000, E=12 3) So I conclude a) More RAM takes much longer b) More RAM significantly increases B2. If I allocate more RAM (339 GB was the largest mprime would accept), that can a) Take longer (more GHz days) b) Increase B2 which has a better chance of finding a factor. c) Increase access time to the RAM, if the amount of RAM exceeds that local to a CPU. A calculator at https://www.mersenne.ca/prob.php?exp...747177&prob=30 indicates the time and RAM for any given probability of finding a factor. But it seems to be outdated, as the RAM I used on that exponent was considerably more than the calculator gives, so I think it is probably outdated. So I'm still puzzled on how to work out optimal settings for RAM. I'm not convinced that retesting old exponents with known factors is that helpful, but I may be wrong. What seems more important is a) The probability of finding a factor given particular value of B1 and B2. b) The time on my computer (not GHz days) to work with those values of B1 and B2. Given the time to do the P1 test, and the fact sizes of exponents that need testing will keep increases, it is probably impractical to build up statistically significant data based on the number of times I find a factor. I generally run the PRP tests so that one exponent is around 50% complete when the other starts. So the chances of two exponents both doing P1 tests at the same time is pretty close to zero. Last fiddled with by drkirkby on 20210507 at 09:15 

20210507, 09:03  #6  
Jun 2003
1001101100110_{2} Posts 
Quote:
Quote:
Quote:
Give the maximum amount of RAM you can spare. Let the software manage the rest. 

20210507, 09:44  #7 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
3×29×59 Posts 
Again, use the reference info. P1 bounds And read and understand https://www.mersenne.org/various/math.php
Also your post was vague. Thread title does not indicate your interest is specifically in mprime or prime95. Last fiddled with by kriesel on 20210507 at 09:48 
20210507, 10:57  #8  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
2×3×5×7 Posts 
Quote:
Code:
[dkirkby@jackdaw ~]$ mprime v Mersenne Prime Test Program: Linux64,Prime95,v30.6,build 4 Last fiddled with by drkirkby on 20210507 at 11:00 

20210507, 15:11  #9 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
5133_{10} Posts 
I meant as opposed to P1 factoring in Gpuowl, CUDAPm1, gmpecm, something in perl or in Pari/GP, etc.
Attachment of https://www.mersenneforum.org/showpo...91&postcount=2 is basic knowledge and shows multiple programs for most computation types, including P1. Mprime/prime95 are great but not the whole story. From the readme.txt packaged with mprime or prime95: Code:
FILE LIST  readme.txt This file. prime95.exe The windows program to trial factor and primality test Mersenne numbers. mprime The Linux program to trial factor and primality test Mersenne numbers. Last fiddled with by kriesel on 20210507 at 15:40 
20210507, 15:38  #10  
Jul 2003
wear a mask
11001001101_{2} Posts 
Quote:
A few questions to help us better answer your questions. 1. You have two cpus. Are you running two instances of mprime? 2. You mentioned mprime. That means you're using linux, right? 3. What type of P1 work would you like to do? Wavefront P1 (to help the search for the next large prime), 100M P1 (to help find the $$$prize winning large prime) or to participate in some other factoring challenge? My generic suggestion would be to a. Determine what type of work you would like to do and reserve/acquire a good sized set (many days worth of work) of assignments. Choose appropriate B1 bounds for the tasks. b. Split the assignments over two worktodo files and run each of the files with a separate instance of mprime. c. In each version of mprime, allocate less than half of your system RAM. d. Monitor your results for a day, then adjust the B1 bounds or the allocated RAM. Repeat this step until you are happy with system utilization, work credits, whatever your goal is. Last fiddled with by masser on 20210507 at 15:39 

20210507, 19:18  #11  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
2×3×5×7 Posts 
Quote:
Yes. CentOS 7.9. Quote:
Quote:
https://www.mersenne.org/thresholds/ Someone bought this to my attention a few days ago, so now I have been allocated a couple of category 1 exponents. Quote:
Quote:
https://www.mersenne.ca/prob.php?exp...747177&prob=30 could be updated to accurately reflect the probability of finding a factor with the current algorithm, I could probably work out a sweet spot. I might find this becomes irrelevant if I offer mprime 339 GB (maximum it will accept on my machine), but it actually chooses to use less than half my RAM (192 GB). The next exponent I commence will be this one, in about 13 hours from now. https://www.mersenne.org/report_expo...0000000&full=1 That has already been P1 factored to B1=860 000, B2=17 415 000, E=6. I don't know whether mprime will just start straight on the PRP test, or perhaps do some more P1 factoring with a larger value of B2. Last fiddled with by drkirkby on 20210507 at 19:19 

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