20220614, 05:46  #67 
Einyen
Dec 2003
Denmark
2×1,693 Posts 
This works for P1 and P+1 I tested long ago on composite numbers I constructed. I *think* it works for ECM as well, please correct me if that is not the case:
You can run stage2 in many stages or even random segments. For example if you run stage 1 with B1=1e6 and save it to a file, you can resume from that file and run any stage2 range you fancy. For example B2=3e134e13 and if you are super lucky that the largest factor of P1 / P+1 (or the elliptic curve in case of ECM) is in that range, then you will find the factor, even though you did not run any stage2 from 1e6 to 3e13. This is more useful for P1 / P+1 than for ECM, since there is only 1 P1 run needed or only a few runs needed with P+1 (50% chance for each run). For ECM where you have only a tiny chance for each curve it is probably not very useful to spend a lot of time on each curve messing around with a lot of different stage2 segments. Last fiddled with by ATH on 20220614 at 05:47 
20220615, 12:33  #68 
Aug 2002
8511_{10} Posts 

20220615, 13:19  #69 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
2^{3}×857 Posts 
Dunno, but to summarize a PM conversation with Gordon, after I was able to run gmpecm with memory usage > 19G on Win7 (both stages on gmpecm), Gordon was able to on his system too, so it may depend on details of how gmpecm is run, and more testing is planned. (I haven't tried the prime95 stage 1 / gmpecm stage 2 sequence that gave the issue originally seen by Gordon on Win7.) The issue may appear when specifying B2, or splitting the stages to two different softwares, or both.

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