Home Original page

[Python-Dev] Decimal news: speedup and stabilization

Nick Coghlan ncoghlan at gmail.com
Sat Nov 24 05:56:15 CET 2007 
Facundo Batista wrote:
> Mark Dickinson found out that a lot of time was lost internally in
> decimal.py when dealing with the Decimal mantissas.
> 
> He changed the way that mantissa was stored, from a tuple of ints, to
> a plain string (each character a digit). This achieved a speedup of
> around a 40%!!!

Given the frequent conversion to and from long integers needed to 
actually do the calculations, I can actually see how that would be the 
case. Excellent news.

Did you change the Decimal repr to use the same format for the mantissa?

> 
> Three notes:
> 
> - The speedup was measured using two tools I created [*], one
> basically tries a lot of use cases, the other use the specification
> test cases. Both generate a .py which actually measures the times.

Could you also check the performance gain against the telco benchmark 
which is in the sandbox? [1]

The 10-number file is checked into svn along with the test script, and 
the million-number file is available from Cowlishaw's decimal site [2].

Cheers,
Nick.

[1] http://svn.python.org/projects/sandbox/trunk/decimal/telco/
[2] http://www2.hursley.ibm.com/decimal/telco.html

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
---------------------------------------------------------------
             http://www.boredomandlaziness.org
More information about the Python-Dev mailing list