----- Original Message ----- From: "George Woltman" <[EMAIL PROTECTED]> To: "Gerry Snyder" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Saturday, December 01, 2001 10:39 PM Subject: Re: Mersenne: Re: Factoring benefit/cost ratio
> I prefer a factor to a double-check. But it is hard to quantify "prefer" in a > mathematical formula for computing trial factoring limits. Prime95 uses > the formula: cost_of_factoring must be less than chance_of_finding_a_factor > times 2.03 * the cost_of_an_LL_test. Shouldn't that be 1.015 for double-checking assignments? Also does the cost part of the calculation recognise the increased cost of trial-factorisation after 2^64? I've noticed on occasion that I've had to do an extra round of trial factoring before proceeding with an doublecheck. This indicates that previous factorisation has been non-optimal, or have the estimates for the relative costs of factoring vs. LL testing changed with the introduction of new hardware? Finally if P-1 factorisation were to be spun off into a separate work unit, then the optimal arangement would be to trial factor while cost_of_trial_factoring * chance_of_P-1_factoring is less than cost_of_P-1_factoring * chance_of_trial_factoring. Then P-1 factorise. Then complete trial factorisation according to the above formula. > -- George Daran G. _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
