Thread: Head, meet wall
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Old 2007-03-05, 18:15   #8
ewmayer's Avatar
Sep 2002
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Originally Posted by akruppa View Post
GMP-ECM has a trial division option: -t <limit>
It is quite useful for getting rid of really small factors before actual ECM starts up. It also has a -primetest option, which checks inputs for primality, but you have to specify it - there's no such check by default.
Alex, I suggest you make -primetest the default in future releases. Given how cheap a PRP test is and that the needed functionality already is there, no good reason not to always do one prior to starting serious crunching.

(NFS program authors take not as well.)

This will also catch any occurrences of composites due to potential other reasons, e.g. candidate-processing scripts in some kind of automated factoring flow, data corruption in a networked effort, etc.

Sure, it's not unreasonable to assume users of such code will do such a test themselves, but like I said if the functionality is already there or is trivial to add...
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