It's all on these two functions. Three most frequently used operations of Num (ModP x) are (+) (-) (*)，each of them will at least call p2num once(to get the modulus), in addition multiplication will call montgKeys. usual implementation do both in constant time: p2num is written as number literal with type "Integral a=>a", so a reasonable implementation should handle these two function in constant time(in amortized time, of course). On Nov 7, 2011 2:27 PM, "Ivan Lazar Miljenovic" <ivan.miljenovic@gmail.com> wrote:
On 7 November 2011 16:54, Bin Jin <bjin1990@gmail.com> wrote:
The actual time to calculate p2num and montgKeys are both O(log P). What I'm looking is a constant time lookup.
Are these two functions CPU bottlenecks as revealed by profiling? If not, then you're probably over-optimising.
Note that if O(1) lookup is really required, then that implies you use a static array, which requires you to pre-populate such an array with all possible values.
-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com