[Python-Dev] Decimal in C status (was Re: draft 3.1 releaseschedule)

Nick Coghlan ncoghlan at gmail.com
Tue Mar 10 14:58:28 CET 2009

Raymond Hettinger wrote:
> [Nick Coghlan]
>>> What about decimal-in-C, by the way? Is anyone still working on it?
> I'm seeking funding for the project. If it is forthcoming, I intend to do
> a pure C version that simply implements the spec and then adds
> wrappers for the pure python interface.  That will save the cost
> of constantly creating and modifying many pyobjects that currently
> arise during intermediate calculations. 
> It's possible to focus just of the mantissa calculations but the cost of
> the actual arithmetic work is swapped by the overhead of managing
> contexts, checking for special values, and memory allocations.
> Without addressing those, I think decimal will remain critically
> performance challenged compared to native floats (decimals
> will never be that fast, but they can get close enough to make
> them a viable alternative for many kinds of work).

I actually agree with all that, but do you agree the mantissa work is
still worthwhile in the near term (i.e. 3.1) to address the 25% or so
slowdown between decimal in 2.x (with the mantissa as an 8-bit str) and
decimal in 3.0 (with the mantissa as a unicode str, because using a
bytes object to store the digits is actually slower due to the lack of a
bytes->long fast path)?


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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