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Date: Wed, 6 May 2015 23:55:56 +1000
Subject: Re: Throw the cat among the pigeons
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:90057

On Wed, May 6, 2015 at 11:12 PM, Dave Angel <davea@davea.name> wrote:
> I had guessed that the order of multiplication would make a big difference,
> once the product started getting bigger than the machine word size.
>
> Reason I thought that is that if you multiply starting at the top value (and
> end with multiplying by 2) you're spending more of the time multiplying
> big-ints.
>
> That's why I made sure that both Cecil's and my implementations were
> counting up, so that wouldn't be a distinction.
>
> I'm still puzzled, as it seems your results imply that big-int*int is faster
> than int*int where the product is also int.

Are you using Python 2 or Python 3 for your testing? In Py3, there's
no type difference, and barely no performance difference as you cross
the word-size boundary. (Bigger numbers are a bit slower to work with,
but not hugely.)

ChrisA