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Re: Code optimization

  • To: mathgroup at
  • Subject: [mg109773] Re: Code optimization
  • From: "M.Roellig" <markus.roellig at>
  • Date: Sun, 16 May 2010 08:51:59 -0400 (EDT)
  • References: <hsofh5$3if$>


Instead of writing

 foo =(expression 1)/(obscenely complex expression )+ (expression 2)/
(obscenely complex expression )

it pays out to do something like :

denominator = obscenely complex expression ;

foo=(expression 1)/denominator + (expression 2)/denominator

Mathematica will calculate the complex expression once and store the
result in denominator
and only use that for later occurances of denominator.

If you use

denominator := obscenely complex expression ;

instead, it will recalculate the complex stuff each time denominator
is encountered.


> foo =(expression 1)/denominator + (expression 2)/denominator
> where "denominator" is itself a complex expression. Is it worthwhile for
> me to compute "denominator" once and use it explicitly in foo, or will
> Mathematica cleverly deduce that it needs to be computed only once?
> My guess is that Mathematica is an interpreter so it will not optimize the code.
> Steve Gray

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