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Re^2: OT: Finding Factor Closest To Square Root

by QM (Parson)
on Feb 20, 2005 at 07:20 UTC ( #432845=note: print w/replies, xml ) Need Help??

in reply to Re: OT: Finding Factor Closest To Square Root
in thread OT: Finding Factor Closest To Square Root

Yes, but this still takes a long time for large prime N, as it has to count down from sqrt(N) to 1.

It would go twice as fast if we checked N%2==0. It would go six times as fast if we checked for N%3==0 also. Perhaps using GCD(N,sqrt(N)#) (where N# is the primorial of N) would improve the situation? The problem then becomes one of generating all primes upto sqrt(N), where we could cheat and just have a big list precomputed.

...Better yet, would a quick test of N for primality solve the problem of prime N?

Quantum Mechanics: The dreams stuff is made of

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