20180218, 23:30  #1 
Sep 2002
Oeiras, Portugal
2·727 Posts 
P1 savefiles
Hi all,
I have recently started running some P1 tests on small exponents, trying to dig out some more new factors (one found already!... ). I noticed that the savefiles, including the .bu ones, are left in the working directory when the test finishes. Disk space is not an issue, but still I found it funny that the files are not erased, like in the other work types. It´s a long time now since I ran P1 on a regular basis, and I vaguely remember there was a reason for this to be done in this particular work type. Would someone care to enlighten me on this subject? Thx in advance. Last fiddled with by lycorn on 20180218 at 23:31 
20180218, 23:55  #2 
Sep 2003
2^{2}·647 Posts 
If you run a new P−1 test with a higher B1, it will use the old savefile to resume the calculation, instead of starting from scratch.

20180219, 09:33  #3 
Sep 2002
Oeiras, Portugal
10110101110_{2} Posts 
Fine. That´s interesting. I´ll give it a try, for sure.
Thank you very much for your prompt answer. Last fiddled with by lycorn on 20180219 at 09:34 
20180219, 14:57  #4 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
1001000000011_{2} Posts 
I tried this lately and observed the following:
From the PC with the save files I ran another P1 with both B1 and B2 larger. Stage 1 continued from the last B1 value running proportionately faster. Stage 2 seemed to rerun entirely based on its elapsed run time. Is this as designed? PS once a P1 completes you only need to keep the main backup file; the one without a .bu extension. Last fiddled with by petrw1 on 20180219 at 14:59 
20180219, 15:54  #5 
Jun 2003
4939_{10} Posts 

20180219, 16:43  #6 
Einyen
Dec 2003
Denmark
2×1,543 Posts 
With GMPECM I have run huge P1 curves doing both B1 and B2 in stages. You only need to run stage1 incrementally, then when you reach some desired B1 for example 1e9, you can run any stage2 intervals you like on that stage1 file in any order, like 1e111e12 then 1e101e11 or whatever.
In Prime95 though I only think it allows you to run stage2 incrementally from the current B1 and up. Last fiddled with by ATH on 20180219 at 16:44 
20180219, 20:28  #7  
Sep 2002
Oeiras, Portugal
2656_{8} Posts 
Quote:
Also, what range of exponents have you tried with GMPECM? I have done a lot of work with GMPECM, not P1 testing, though, and it only pays for really small (< 30,000) exponents. I don´t know how it goes for P1. 

20180219, 22:52  #8  
Einyen
Dec 2003
Denmark
2·1,543 Posts 
Quote:
Here is a random example: Code:
4437613266767947934612882360369779858184509124945083658308877174193087878506071380993 = 5416454354354334983409847 * 819283792763897632487263487263897276392763982763928379283719 and 5416454354354334983409846 = 2*3*71*3769*13180897*255937771847 If I run stage1 with only B1=10^7 and save to a file, then resume from that file doing B2=250e9 to 260e9 it does not find the factor. But when I do stage1 to B1=2*10^7 and save to a new file and resume that file doing stage2 B2=250e9 to 260e9 it finds the factor. (see output in attached file) So it finds the factor even if I skipped doing stage2 from B2=2*10^7 to 250e9, as long as you are lucky your stage2 interval contains the largest P1 factor, it does not matter. This also applies to P+1 and ECM (though for ECM it is not a factor but the curve group order depending on the sigma for the curve). But each B1 value has it own separate B2"space", so you have to take B1 as high as you want to go before starting to do stage2, or you have to do stage2 over again when you increase B1. I did not do P1 on a lot of Mersenne numbers, I just did some big P1 on special numbers like F12, M1277, different stages of HP49 and EuclidMullin EM52 and such. By big/huge P1 I did not mean big/huge Mersenne numbers, but I meant B1~ 10^12 and B2 ~ 10^17  10^18. Last fiddled with by ATH on 20180219 at 23:06 

20180219, 23:50  #9 
Sep 2002
Oeiras, Portugal
2×727 Posts 
Thanks for the very useful explanation.
I´ll try to find the time to test several combinations of B1 / B2 and different exponent ranges. 
20180221, 03:18  #10 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
3·29·53 Posts 
So it seems a n efficient method to maximize factors and minimize work (ummm PC work...actually more manual labor) is to start with a relatively low B1 only...and increment it in steps to a desired maximum or until it finds a factor and only run B2 as a last step if necessary

20180221, 05:00  #11 
"Curtis"
Feb 2005
Riverside, CA
2·5^{3}·19 Posts 
Doesn't stage 1 spit out a factor when it's found, rather than at the end of the stage? I mean, you can just run a single large B1 rather than a bunch of iterations working up to the large B1 (if you're not going to do stage 2 at any intermediate B1, that is).
Doing a single run should spit out factors just as quickly as iterating B1 upward at least, that's how GMPECM behaves. Perhaps P95 isn't the same? 
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