2013-11-28, 21:04 | #1 |
Feb 2012
Paris, France
A1_{16} Posts |
Having a hard time finding a polynomial for a C138
I'm currently searching a polynomial for a C138 using msieve 1.52 (SVN 942)
GPU, the best thing I could get is e = 2.831e-011 whereas the expected e is from 2.93e-011 to > 3.37e-011. Out of curiosity I ran msieve 1.51 and it says expecting poly E from 2.55e-011 to > 2.93e-011. Any advice(s) would be appreciated. Note: I had two instances of msieve 1.52 running on two GPUs, the default stage 2 norm is 1.73e+019, on the various runs I've made I set "stage2_norm=X" with X=3e+018, 7e18, 9e18. |
2013-11-29, 16:01 | #2 |
"Curtis"
Feb 2005
Riverside, CA
1010000100010_{2} Posts |
The "expected" scores are an estimate, which at certain sizes is difficult to achieve- you have found such a size. You found a poly with a score in the range listed from v1.51- why did you say you are having a hard time, when you do actually have a poly?
If the number takes 3 days to sieve, does it matter if you've hit the target score? Would you feel better about your GPUs if you spent 36 hr finding a poly in the v1.52 window that sieves the job 4 hrs faster than the poly you have now? |
2013-11-29, 21:56 | #3 | ||
Feb 2012
Paris, France
7×23 Posts |
Quote:
It's actually worse than that, I can do sieving + LA in less than 18 hours Quote:
Thank you for your help. |
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2013-11-30, 03:16 | #4 |
Tribal Bullet
Oct 2004
3·1,181 Posts |
There is another 'dead zone' around 150 digits.
You do have to be careful that polynomial selection not take much longer than it is worth, especially for jobs where the sieving would not take long even for a bad polynomial. The library tries to limit the total time spent searching for polynomials but that's not as simple as it sounds. The measurement of E value was changed in v1.52 to match the scores produced by the CADO tools, but the process of selecting polynomials has not changed otherwise. |
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