This web mail archive is frozen.
This page is part of a frozen web archive of this mailing list.
You can still navigate around this archive, but know that no new mails
have been added to it since July of 2016.
Click here to be taken to the new web archives of this list; it includes all the mails that are in this frozen archive plus all new mails that have been sent to the list since it was migrated to the new archives.
On Sun, 2009-07-12 at 19:49 -0500, Yin Feng wrote:
> Can you give me a further explanation about why results are different
> when it ran it on mutiprocessors against single processor?
Floating point number are problematical for a number of reasons, they
are only *approximations of real numbers because of the limited
precision. This means that when you do calculations with floating point
numbers the you end up with approximations of the answers (because you
only really had a approximation of the question).
In parallel computing you find that the route taken to reach an answer
is different to that taken in serial computing and hence you get
different errors so the eventual answer is different. Furthermore
you'll quite likely find that you get different answers running at
different scales, depending on how you spread out your job.
Unfortunately it's a fundamental limitation of classical computing and
one that people have learned to live with.
Ashley Pittman, Bath, UK.
Padb - A parallel job inspection tool for cluster computing