On 14 Jun 99, at 6:41, lrwiman wrote:
> We will of course have to check factors considerably further than we are doing
> on our current exponent range (due to the increased LL iteration time.)
Yes - on the principle that it's worthwhile to spend 5% to 10% of the
LL testing time attemptimg to find at least one factor before we run
a LL test, the pre-factoring should be run for 3 or 4 weeks per
exponent first (assuming PIII-500 class power). At a rough guess,
that's up to 2^66 or 2^67, but we don't have any benchmarks yet.
> think that someone (Brian...?) did test for all 10,000,000 digit primes
> <36,000,000 for factors <2^40. Maybe George can add these to his database, or
> something.
George advised "don't bother" but I did it anyway. Just for fun. But
I checked the results carefully enough to be sure I'm not making an
idiot of myself.
You can find the results in standard format in the /gimps/DecaMega
directory on my anon ftp server lettuce.edsc.ulst.ac.uk
Of course, trial factoring to 2^40 is very quick - I spent only about
2 (PII-350) CPU hours spread over all 159,975 candidate exponents in
the range I selected. But that's enough to eliminate a third of them.
If anyone's _really_ keen I could send them the source of the program
I used (needs MS VC++). It's reasonably efficient & will go to 2^63.
Exponents in the 30 millions are not acceptable to Prime95 v18 and
its derivatives.
The factors found were verified against a much simpler program run on
an Alpha & I have lots of confidence in them.
Regards
Brian Beesley
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