Thread: Dodecaproths
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Old 2006-01-17, 23:05   #40
Kosmaj's Avatar
Nov 2003

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Two questions/suggestions.

Originally Posted by R. Gerbicz
We are searching in remainder classes this is "g" in the program, we are searching for k, where k==g mod step, here step is the product of the first x primes.
(1)While doing this are you using the fact that k must be a multiple of several first primes, for example, for DodecaProths k must be an odd multiple of 3*5*7 for all n, while for some n (like 58 above) it also must be a multiple of 11. Then you can increase step by including up to 3 (or 4) more primes. By doing this you can also reduce the values kept in internal variables, for example instead of k you can keep k/105 and thus increase the range of k while using the same int type.

(2) In the second step are you sure you are not over-sieving? It is possible that sieving above a certain value removes only a small portion of candidates and is therefore more time consuming than prp test because modular division ("%" in C) requires many cpu cycles. Maybe in case of DodecaProths we can stop sieving at 10000 instead of going to 32000 (there are more than 2200 primes between 10k and 32k)?
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