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Tue Oct 16 18:55:31 CEST 2007 · http://mail.python.org/pipermail/python-dev/2007-October/074941.html

Mark Dickinson wrote:

>I'm almost sure that adding 40000 digit numbers together is not what
>Decimal was intended to be used for, but it still seems unreasonable
>that it takes almost 5 seconds to do such an addition.  The reason for
>the quadratic behaviour is that almost all the arithmetic routines in
>decimal.py, at some point, convert the coefficient of their
>argument(s) from a tuple of digits to a Python integer, and then do
>the reverse conversion to get a Decimal result;  both of these
>conversions (tuple of digits <-> integer) take time quadratic in the
>size of the tuple/integer.   This means that multiplication of
>Decimals is also quadratic time, even though it makes use of Python's
>subquadratic Karatsuba multiplication.
>  
>
Oh right, my mistake :> -- I looked at python code, but I forgot about 
conversion ;).

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[Python-Dev] C Decimal - is there any interest?