# Fast decimal arithmetic module released

Discussion in 'Python' started by Mark Dickinson, Oct 2, 2009.

1. ### Mark DickinsonGuest

On Oct 2, 8:53 pm, Stefan Krah <> wrote:
> Hi,
>
> today I have released the following packages for fast arbitrary precision
> decimal arithmetic:
>

[...]

Nice! I'd been wondering how you'd been finding all those decimal.py
bugs. Now I know.

--
Mark

Mark Dickinson, Oct 2, 2009

2. ### Stefan KrahGuest

Hi,

today I have released the following packages for fast arbitrary precision
decimal arithmetic:

1. libmpdec
============

Libmpdec is a C (C++ ready) library for arbitrary precision decimal
arithmetic. It is a complete implementation of Mike Cowlishaw's
General Decimal Arithmetic specification.

2. fastdec.so
==============

Fastdec.so is a Python C module with the same functionality as decimal.py.
With some restrictions, code written for for decimal.py should work
identically.

3. deccheck.py
===============

deccheck.py performs redundant calculations using both decimal.py and
fastdec.so. For each calculation the results of both modules are compared
and an exception is raised if they differ. This module was mainly developed
for testing, but could in principle be used for redundant calculations.

Correctness
============

Libmpdec passes IBM's official test suite and a multitude of additional tests.
Fastdec.so passes (with minor modifications) all Python unit tests. When run
directly, deccheck.py performs very exhaustive tests that compare fastdec.so
with decimal.py.

All tests complete successfully under Valgrind.

Speed
======

In a couple of initial benchmarks, libmpdec compares very well against
decNumber and the Intel decimal library. For very large numbers, the speed
is roughly the same as the speed of the apfloat library.

Fastdec.so compares quite well against gmpy and even native Python floats.
In the benchmarks, it is significantly faster than Java's BigDecimal class.

Portability
============

All tests have been completed on Linux 64/32-bit, Windows 64/32-bit, OpenSolaris
32-bit, OpenBSD 32-bit and Debian Mips 32-bit. For 32-bit platforms there is
a pure ANSI C version, 64 bit platforms require a couple of asm lines.

Further information and downloads at:

http://www.bytereef.org/libmpdec.html

Stefan Krah

Stefan Krah, Oct 2, 2009

3. ### Raymond HettingerGuest

[Stefan Krah]
> today I have released the following packages for fast arbitrary precision
> decimal arithmetic:

Nice.

Raymond

Raymond Hettinger, Oct 3, 2009
4. ### Stefan KrahGuest

Mark Dickinson <> wrote:
> On Oct 2, 8:53 pm, Stefan Krah <> wrote:
> > Hi,
> >
> > today I have released the following packages for fast arbitrary precision
> > decimal arithmetic:
> >

> [...]
>
> Nice! I'd been wondering how you'd been finding all those decimal.py
> bugs. Now I know.

Thanks! Yes, actually deccheck.py deserves the credit.

Stefan Krah

Stefan Krah, Oct 3, 2009

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