mersenneforum.org Multiplication in cyclotomic rings
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 2009-01-23, 10:05 #1 wpolly     Sep 2002 Vienna, Austria 3·73 Posts Multiplication in cyclotomic rings I am working on an implementation of the APR-CL algorithm, and encountered the problem of efficient multiplication in $Z[\zeta_{p^k}]$. The original paper of Cohen and Lenstra only gives the cases $p^k=3,4,5,7,8,11,16$. Is there any general method to construct an multiplication algorithm which takes $O(p^k)$ integer-multiplies?
2009-01-23, 22:08   #2
R.D. Silverman

Nov 2003

22·5·373 Posts

Quote:
 Originally Posted by wpolly I am working on an implementation of the APR-CL algorithm, and encountered the problem of efficient multiplication in $Z[\zeta_{p^k}]$. The original paper of Cohen and Lenstra only gives the cases $p^k=3,4,5,7,8,11,16$. Is there any general method to construct an multiplication algorithm which takes $O(p^k)$ integer-multiplies?
AFAIK, it is like FFT schemes for non powers of two length; Each multiplication
scheme gets specially constructed. Wieb Bosma's dissertation is a good
source of information on this subject. When I did my implementation many
years ago, I added k = 9, 17, 18, and 25, but I worked out the schemes
using a lot of trial-and-error and a lot of help from a CAS.

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