## ECM found factors, why so many repeats?

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Tom Poleski
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### ECM found factors, why so many repeats?

I'm very curious to know why, at the page: http://www.rechenkraft.net/yoyo//y_factors_ecm.php it repeats the same factors found, over and over again. Why is this happening?

yoyo
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### Re: ECM found factors, why so many repeats?

To find a factor thousands of workunits have to be computed. This is done in parallel by hundreds of user. So if an easy factor is found it is possible, that the factor is found by many user in parallel. As fast as the server gets a found factor it cancels all not yet sent out workunits and if a client is connected it tells him to abort all not yet started workunits.
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Tom Poleski
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### Re: ECM found factors, why so many repeats?

yoyo hat geschrieben:To find a factor thousands of workunits have to be computed. This is done in parallel by hundreds of user. So if an easy factor is found it is possible, that the factor is found by many user in parallel. As fast as the server gets a found factor it cancels all not yet sent out workunits and if a client is connected it tells him to abort all not yet started workunits.
But, as far as I understand, each workunit should be attempting to compute a different range, no? Otherwise would it not be a waste of resources? If multiple computers find the same factor in parallel, doesn't that mean that multiple computers are computing the same workunit?? Or at least, performing the same calculation on the same range of data across multiple work units?
Perhaps I just do not understand enough about how the mathematics works behind it. Thank you for the reply.

yoyo
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### Re: ECM found factors, why so many repeats?

Workunits are NOT splited based on different ranges!
ECM, the eliptic curve method, is a trial factoring method. For a batch we have to run different trials, all starting with a different random seed.
So all computations are different, they are different trials. For "easy" factors it is therefore possible that with different random seeds the same factor is found.
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Tom Poleski
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Beiträge: 3
Registriert: 03.12.2018 08:36

### Re: ECM found factors, why so many repeats?

yoyo hat geschrieben:Workunits are NOT splited based on different ranges!
ECM, the eliptic curve method, is a trial factoring method. For a batch we have to run different trials, all starting with a different random seed.
So all computations are different, they are different trials. For "easy" factors it is therefore possible that with different random seeds the same factor is found.
I understand, thank you.
May I just ask though.. what makes a factor "easy"?

yoyo
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### Re: ECM found factors, why so many repeats?

A small factor, below 30 or 40 digits.
HILF mit im Rechenkraft-WiKi, dies gibts zu tun.
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