[pypy-dev] algorithm used for float -> str conversion

Amaury Forgeot d'Arc amauryfa at gmail.com
Thu Jun 30 10:24:00 CEST 2011


2011/6/30 Alexandre Fayolle <alexandre.fayolle at logilab.fr>:
> I just came across http://www.serpentine.com/blog/2011/06/29/here-be-dragons-
> advances-in-problems-you-didnt-even-know-you-had/ which talk about a paper
> submitted last year about a fast float -> str conversion routine. I don't know
> what is currently used in pypy (or in Python actually), probably the
> underlying libc's implementation, but this could be something interesting for
> people writing lots of floats in csv files.

Someone reported the same post on the cpython tracker,
and I've just filed a separate issue about this idea.

Note that cpython2.7 (and pypy 1.5) already uses a specific algorithm
to convert float to strings: a slightly customized version of David Gay's
dtoa.c: http://www.netlib.org/fp/dtoa.c
it is already faster and more accurate than many libc implementations.

Amaury Forgeot d'Arc

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