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

2·1,811 Posts

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)?
Kosmaj is offline