Talk:Find largest left truncatable prime in a given base: Difference between revisions
Talk:Find largest left truncatable prime in a given base (view source)
Revision as of 11:55, 9 April 2017
, 7 years ago→Discrepancy in auxiliary output
(→Number of left truncatable primes in a given base: Discrepancy in some auxiliary output.) |
|||
Line 1,220:
</pre>
The Fortran version checks for possible factors up to 2800 by bignumber division before it starts on the MR process. [[User:Dinosaur|Dinosaur]] ([[User talk:Dinosaur|talk]]) 06:11, 9 April 2017 (UTC)
::One of the purposes of this task is to highlight problems with primality testing of a large number of large numbers. If you are using MR these are twofold: first being able to randomly select prime numbers fairly across the range 3 to the large number; second the number of prime numbers you are going to try. In the worst case for a single trial there is a 1 in 4 (usual case more like 1 in 50) chance that the large number is actually composite. This chance rapidly decreases with trials, but so does the time taken. So the recommendation is to do quick trials allowing some non prime candidates to be propagated, then a thorough check of you final candidate(s) that it is indeed a left truncatable prime.--[[User:Nigel Galloway|Nigel Galloway]] ([[User talk:Nigel Galloway|talk]]) 11:55, 9 April 2017 (UTC)
==Odd base optimization==
| |||