[Jprogramming] Precision of modular multiplication of quite large numbers

['Mike Day' via Programming]

Yes,  I did have a look,  especially as one approach to the problem I 
was examining was
to construct a set of coefficients modulo M based on polynomial 
multiplication.

eg
(1 + ax)(1 + bx)(a+cx) .... = 1 + (a+b+c+...)x + (ab + bc + ca + ...)x^2 
+ ...
for which we should be able to use
add =: M&|@+
by =: M&|@*
ppr  =:  add//.@(by/)    NB. adapted from the Wiki essay
with
ppr/ 1,. a,b,c,...
but it looked to me as if I'd have to invoke the fft multiplier in 
scalar fashion.
I'm happy to be proved wrong.

But I'm probably on the wrong tack for the problem as a whole!

Thanks, Raul
Mike

On 08/05/2017 14:19, Raul Miller wrote:
> On Mon, May 8, 2017 at 4:43 AM, 'Mike Day' via Programming
> <programming at jsoftware.com> wrote:
>> Is there a better way to do modulus multiply with largish arguments?
> Hypothetically speaking, you might be able to do something based on
> http://code.jsoftware.com/wiki/Essays/FFT
>
> I hope this helps,
>


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