Ruby to solve a physics question

I am trying to solve one of my graduate level physics problems with
ruby…
Here is what I have so far…

a6=0.0
for n1 in -10…10
for n2 in -10…10
for n3 in -10…10
if n1!=0 and n2!=0 and n3!=0
p=Math.sqrt(n12+n22+n3**2+n1n2/1.414+n1n3/1.41+n2*n3/1.414)
a6+=(1/p)**6
end
end
end
end
puts a6

What I’ve got here is a 10x10x10 face-centered cubic lattice of atoms.
What I want to do is find this constant a6= sum(1/Pij)**6. From a
starting point I want the distance to every other atom location point in
the structure, meanwhile inversing and power to the sixth each distance.
Then I want to add all those up. This should return 14.4???

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Am 14.09.2011 02:34, schrieb thiess cunningham:

I am trying to solve one of my graduate level physics problems
with ruby…

Hi thiess,

this is the wxRuby mailinglist, related to the wxRuby GUI toolkit.
Your question should better be served on ruby-talk. Go to
http://www.ruby-forum.com/forum/ruby for posting there.

location point in the structure, meanwhile inversing and power to
the sixth each distance. Then I want to add all those up. This
should return 14.4???

I’m by no means someone who has any knowledge on how atom physics
work, but a few notes on your code:

  • Don’t use “for” in Ruby. There’s the #each method that is the
    correct idiom for this. And four your specific case you should use:
    -10.upto(10) do |nx| … end

  • The test against zero can be made much more readable with the
    Methods Integer#zero? and Integer#nonzero?

  • I’m not willing to dig into the giant term you pass to Math.sqrt.

  • From a first glance, you might want to have a look at the
    Enumerable#inject method, which you can use to easily sum up things
    that are computed the same way.
  • Be aware that doing math with floating-point numbers is always
    dangerous as they’re not exact. The further you continue to compute
    with floating-point results you got, the more unprecise your final
    result will be. If I remember correctly, this is the industry standard
    to blame for this: http://en.wikipedia.org/wiki/IEEE_754-2008

As I noted before, post your question to ruby-talk. It’s not related
to wxRuby in any way.

Vale,
Marvin
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