A reimplementation of MaskedArray

A. M. Archibald peridot.faceted at gmail.com
Thu Nov 9 01:27:38 CST 2006


On 08/11/06, Tim Hochberg <tim.hochberg at ieee.org> wrote:

> It has always been my experience (on various flavors or Pentium) that
> operating on NANs is extremely slow. Does anyone know on what hardware
> NANs are *not* slow? Of course it's always possible I just never notice
> NANs on hardware where they aren't slow.

On an opteron machine I have access to, they appear to be no slower
(and even faster for some transcendental functions) than ordinary
floats:

In [13]: a=zeros(1000000)

In [14]: %time for i in xrange(1000): a += 1.1
CPU times: user 6.87 s, sys: 0.00 s, total: 6.87 s
Wall time: 6.87

In [15]: a *= NaN

In [16]: %time for i in xrange(1000): a += 1.1
CPU times: user 6.86 s, sys: 0.00 s, total: 6.86 s
Wall time: 6.87

On my Pentium M, they are indeed significantly slower (three times? I
didn't really do enough testing to say how much). I am actually rather
offended by this unfair discrimination against a citizen in good
standing of the IEEE floating point community.

A. M. Archibald

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