20161005, 16:59  #1 
Mar 2016
5^{2}×11 Posts 
multiplication and logarithm
A peaceful day for all,
if i want to multiply 100 arising number of f(n)=2*n²1 from n=1001 up to n=1100 and want to have the result modulo f. Does it make sense to use the binary logarithm of f(n) of all terms, adding the results, do a inverse binary log of the result and make then the calculation modulo f ? By the way the use of the logarithm of the arising numbers can it speed up by only regarding the significant different digits ? Would be nice to get some mathematical information Greetings from the primes Bernhard 
20161005, 17:30  #2  
"Forget I exist"
Jul 2009
Dumbassville
20B1_{16} Posts 
Quote:


20161005, 20:13  #3  
Aug 2006
2^{3}·3·13·19 Posts 
Quote:
There are other tricks out there like fast multipoint evaluation which are related. If you need an exact answer you'll need to keep precision essentially the same, so I think the answer is "no". If you can use approximations then there are definitely better methods, depending on your needs. Doing everything like the exact case but keeping fewer digits is simplest but you can probably do a lot better. 

20161006, 10:45  #4 
Mar 2016
113_{16} Posts 
Thanks for your nice answer.
I really appreciate to get some mathematical support from your side. I state that you often give some really good answers, even if the question might be a little bit strange. Thanks and best greetings from the primes Bernhard 
20161006, 13:33  #5 
Aug 2006
5928_{10} Posts 
Glad I could help!

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