Matlab is unable to evaluate very a very long expression

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Attached to this post is a text file containing a very long expression.
I want to evaluate this expression numerically in a Matlab function, i.e. something like this:
function result = (<long lost of all the parameters>)
result = '<this very long expression from the text file>'
end
The computer gets stuck when doing so, not returning a result even after hours of running.
Is there anything I can do to speed up the computation of very long expressions?
  2 Comments
Dominik Hiltbrunner
Dominik Hiltbrunner on 5 Nov 2021
The ^(1/2) terms are in fact generated by Matlab itself, i.e. the long expression also comes from a Matlab file in which my sqrt(...) inputs are then printed in this way. Can I prevent Matlab from doing so?
Every variable in this expression is a scalar, no arrays or matrix operations are performed.

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Accepted Answer

Steven Lord
Steven Lord on 5 Nov 2021
How did you generate this long expression? Did you generate this using Symbolic Math Toolbox? If so consider using matlabFunction to create a function file from this expression (leaving the 'Optimize' option set to its default value of true) and see if the optimization process simplifies the computation of that expression by extracting out some common terms that it can compute once and use repeatedly.
  1 Comment
Dominik Hiltbrunner
Dominik Hiltbrunner on 5 Nov 2021
This is fantastic!
I didn't know about this function before. I used it as follows:
matlabFunction(symbolic_expression,'File','file_name','Optimize',true);
I takes almost 20 minutes to generate/optimize this file, but the computation is incredible fast.
Godd job!

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