On 4/4/2011 1:51 AM, Paul Rubin wrote:

I didn't realize Python used Karatsuba.  The main issue is probably that
Python uses a straightforward portable C implementation that's not
terribly efficient,

but relatively easy for a couple of people to maintain. For (C)Python 3, which no longer has a C int type, I believe changes were focused on making calculations with small integers almost as fast as in 2.x.

(I believe that retaining two implementations internally was considered but rejected. Could be wrong.)

>If you look for the gmpy module, it gives you a way to use gmp from
>Python.  In crypto code (lots of 1024 bit modular exponentials) I think
>I found gmpy to be around 4x faster than Python longs.

For specialized use, specialized gmpy is the way to go.

I am curious how gmpy compares to 3.x ints (longs) with small number calculations like 3+5 or 3*5.


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Terry Jan Reedy

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