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Old 2018-07-18, 04:18   #4
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Dec 2003

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Originally Posted by GP2 View Post
At some point in the future it may become practical to do ECM testing on F33, but not yet. The largest Fermat number for which ECM testing is practicable is F29, with an exponent of about 537 million, which already has a known small factor = 1120049 × 229+2 + 1. I have been doing some ECM testing on it to try to find a second factor, but it takes about 120GB of memory and about a week to do a single ECM curve for F29.
It does not *need* 120GB, because I did a few curves a while back and I only have 32 GB RAM. It took ~95 hours with all 8 cores on Haswell-E assigned to it, but I am not sure how much effect many cores have on ECM tests.
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