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Re: Large number multiplication

References <iv2d7n$ksv$1@speranza.aioe.org>
From Ian Kelly <ian.g.kelly@gmail.com>
Date 2011-07-06 14:02 -0600
Subject Re: Large number multiplication
Newsgroups comp.lang.python
Message-ID <mailman.721.1309982555.1164.python-list@python.org> (permalink)

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On Wed, Jul 6, 2011 at 1:30 PM, Billy Mays <noway@nohow.com> wrote:
> I was looking through the python source and noticed that long multiplication
> is done using the Karatsuba method (O(~n^1.5)) rather than using FFTs O(~n
> log n).  I was wondering if there was a reason the Karatsuba method was
> chosen over the FFT convolution method?

According to Wikipedia:

"""
In practice the Schönhage–Strassen algorithm starts to outperform
older methods such as Karatsuba and Toom–Cook multiplication for
numbers beyond 2**2**15 to 2**2**17 (10,000 to 40,000 decimal digits).
"""

I think most Python users are probably not working with numbers that
large, and if they are, they are probably using specialized numerical
libraries anyway, so there would be little benefit in implementing it
in core.

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Thread

Large number multiplication Billy Mays <noway@nohow.com> - 2011-07-06 15:30 -0400
  Re: Large number multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-06 14:02 -0600
    Re: Large number multiplication Billy Mays <noway@nohow.com> - 2011-07-06 16:21 -0400
      Re: Large number multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-06 14:37 -0600
      Re: Large number multiplication Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2011-07-07 10:30 +0200
        Re: Large number multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-07 09:49 -0600
        Re: Large number multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-07 09:50 -0600
        Re: Large number multiplication casevh <casevh@gmail.com> - 2011-07-07 10:46 -0700
        Re: Large number multiplication Mark Dickinson <mdickinson@enthought.com> - 2011-07-08 00:31 -0700
      Re: Large number multiplication Parerga <nabble.com@bodrato.it> - 2011-07-07 09:00 -0700
  Re: Large number multiplication Christian Heimes <lists@cheimes.de> - 2011-07-06 22:05 +0200
    Re: Large number multiplication Billy Mays <noway@nohow.com> - 2011-07-06 16:15 -0400
      Re: Large number multiplication Christian Heimes <lists@cheimes.de> - 2011-07-06 22:43 +0200
    Re: Large number multiplication Nobody <nobody@nowhere.com> - 2011-07-07 01:33 +0100

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