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Old 2022-09-24, 20:24   #23
Prime95
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Finally, nailed the bugger.

Starting in 30.7, the curve starting point is incorrectly computed on every curve after the first curve. This is due to "leftover state" from stage 2.
The problem is lessened in 30.9 as often you'll see "switching back to FFTlen x" at the end of stage 2.

I do not know how this bug impacts the success rate for ECM finding a factor.
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Old 2022-09-25, 02:09   #24
Prime95
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Download 30.9 build 2 for a fix.
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Old 2022-09-25, 11:19   #25
ATH
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Nice work!

Interesting that it could still find factors and even factors with group orders outside B1/B2.

I guess the different starting points made the curves correspond to different B1/B2 values than was intended?
This is just a guess. I do not really understand the math behind ECM in detail.
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Old 2022-09-25, 14:20   #26
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Quote:
Originally Posted by ATH View Post
I guess the different starting points made the curves correspond to different B1/B2 values than was intended?
This is just a guess. I do not really understand the math behind ECM in detail.
It sounds more likely to me that the different starting points correspond to different sigma values, which change the B1/B2 required to find the factor. For any starting point, you can run the curve to any B1/B2 you want in a similar fashion to P-1.
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Old 2022-10-02, 19:24   #27
Prime95
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Quote:
Originally Posted by Prime95 View Post
Download 30.9 build 2 for a fix.
Grrr, that fix was incomplete. Please download 30.9 build 3. Sorry.
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Old 2022-10-08, 05:30   #28
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Quote:
Originally Posted by Prime95 View Post
Grrr, that fix was incomplete. Please download 30.9 build 3. Sorry.
why bug can also find a factor?
maybe you can find a new algorithm by studying this "bug"
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Old 2022-10-08, 12:01   #29
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Quote:
Originally Posted by bbb120 View Post
why bug can also find a factor?
maybe you can find a new algorithm by studying this "bug"
No, you can't.

ECM curves are determined by a random seed called the sigma value. The bug led to the incorrect sigma being displayed, so ECM was still being run, and was still just as likely to find a factor. Prime95 just wasn't running the exact curves it said it was running.
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Old 2022-10-10, 08:42   #30
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Quote:
Originally Posted by charybdis View Post
No, you can't.
Shhhh! Let him try!
You never know...
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