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Re: [Bug-glpk] expression following = has invalid type
From: |
Chris Matrakidis |
Subject: |
Re: [Bug-glpk] expression following = has invalid type |
Date: |
Sun, 11 Jun 2017 10:34:50 +0300 |
>> Do you have any suggestion(s) to overcome this issue?
>
> You may replace the statement
>
> var R {o in OMEGA} = r[0] + sum{k in 1..n-1} 2*r[k]*cos(k*o);
>
> which is incorrect in MathProg, with the following ones:
>
> var R {o in OMEGA};
> s.t. foo{o in OMEGA}: R[o] = r[0] + sum{k in 1..n-1} 2*r[k]*cos(k*o);
In addition to this, it is a good idea to replace cos(k*o) with something like:
if abs(cos(k*o)) < 1e-9 then 0 else cos(k*o)
otherwise you will get lots of small values that will mess the scaling
of the model. In the example you posted, this leads to a result that
is off by a few orders of magnitude.
Best Regards,
Chris Matrakidis