User talk:Daveb: Difference between revisions

User talk:Daveb (view source)

879 bytes added , 6 October 2012

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 I just open the caliper case, cut the battery trace (which one doesn’t matter), drill two holes to allow the fine (wire wrap) wire to come out the top to a micro-miniature slide switch glued to the top. I always turn the switch off, rather than press some caliper “off” button, and find that a button cell lasts for many years. I would attach a picture if Sparkfun allowed, but it doesn’t. Caliper thickness is unchanged, and the outline is very nearly unchanged.
+|-
+|'''prime number generator'''|| thought || Invert the sieve of Aristophanes, so the data structure holds primes and the next multiple of each prime. Keep the data-structure sorted by the next multiple. When a gap occurs between the current nearest multiple and the next nearest the gap contains prime number(s).
+The algorithm requires sorting subsequent multiples into place.
+If N is the number of discovered primes N, and the size of the primes is S:
+memory use is O(N*S)
+cpu use is O(S*N*N)
+Other ideas:
+* use wheel factorisation of the first M primes to compactly and efficiently represent the impact of these first M primes, where M is chosen so the product of these primes fit in a machine word, and so that the primes less than the product fit in affordable memory.
+* use interval arithmetic to keep track of the intermediate numbers.
+* can it be fitted to hardware?
 |-
 |}
 ==Dumb Ideas==
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