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Old 2019-12-02, 18:40   #3
R.D. Silverman
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Nov 2003

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Originally Posted by VBCurtis View Post
900 core-years computation time (800 sieve, 100 matrix) on 2.1ghz Xeons gold. They observe this job ran 3x faster than would be expected from an extrapolation from RSA-768, and in fact would have been 25% faster on identical hardware than RSA-768 was.

I'd love a more detailed list of parameters! Perhaps a future CADO release will include them in the c240.params default file. :)

For comparison, we ran a C207 Cunningham number 2,2330L in about 60 core-years sieve, which scales really roughly to an estimate of 3840 core-years sieve (6 doublings at 5.5 digits per doubling). The CADO group found a *massive* improvement in sieve speed for large problems! 4 times faster, wowee.

Edit: Their job is so fast that RSA-250 is easily within their reach. Which means that C251 from Euclid-Mullen is within reach, theoretically. I mean, imagine if all NFS work over 200 digits is suddenly twice as fast.....
Truly excellent work. And as you say doubling the speed adds 5-6 digits.

If going after a ~C250, I think 2,1139+ is a better target. It's been waiting for nearly
60 years to be factored. The Euclid-Mullen cofactor is a relative newcomer. Of course
I am biased towards Cunningham numbers.

I'd love to hear the implementation/parameterization details that resulted in their
terrific speed improvement.
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