[Numpy-discussion] ANN: Numexpr 1.3.1 released

Francesc Alted faltet@pytables....
Tue Jun 23 07:23:16 CDT 2009

 Announcing Numexpr 1.3.1

Numexpr is a fast numerical expression evaluator for NumPy.  With it,
expressions that operate on arrays (like "3*a+4*b") are accelerated
and use less memory than doing the same calculation in Python.

This is a maintenance release.  On it, support for the `unit32` type
has been added (it is internally upcasted to 'int64'), as well as a
new `abs()` function (thanks to Pauli Virtanen for the patch).

Also, a little tweaking in the treatment of unaligned arrays on Intel
architectures allowed for up to 2x speedups in computations involving
unaligned arrays.  For example, for multiplying 2 arrays (see the
included ``unaligned-simple.py`` benchmark), figures before the
tweaking were:

NumPy aligned:      0.63 s
NumPy unaligned:    1.66 s
Numexpr aligned:    0.65 s
Numexpr unaligned:  1.09 s

while now they are:

NumPy aligned:      0.63 s
NumPy unaligned:    1.65 s
Numexpr aligned:    0.65 s
Numexpr unaligned:  0.57 s   <-- almost 2x faster than above

You can also see how the unaligned case can be even faster than the
aligned one.  The explanation is that the 'aligned' array was actually
a strided one (actually a column of an structured array), and the
total working data size was a bit larger for this case.

In case you want to know more in detail what has changed in this
version, see:


or have a look at RELEASE_NOTES.txt in the tarball.

Where I can find Numexpr?

The project is hosted at Google code in:


And you can get the packages from PyPI as well:


How it works?



for a detailed description by the original author (David M. Cooke).

Share your experience

Let us know of any bugs, suggestions, gripes, kudos, etc. you may


Francesc Alted

More information about the Numpy-discussion mailing list