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I am using MINLP with NEOS solver, my problem is non-convex and I get this 

Cannot evaluate constraint(s) at starting point

what does this mean and how I can fix it?

1 Answers1

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The meaning is rather obvious. The functions in your constraints cannot be evaluated at the starting point. If the starting point is zero and you have log(x-0.5) in the model you may get a message like this.

The fix is to provide better bounds and a better initial point. How to specify this depends on how you created the model and what modeling tools were used.

Erwin Kalvelagen
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  • thank you, yes my constraints are not defined at 0, so how I can remove 0? –  Oct 16 '19 at 14:00
  • but at zero I have 0/0 is it problem? –  Oct 16 '19 at 14:04
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    x/y can often be protected either setting a lower bound on y (e.g. y>=0.001) or by multiplying expressions by y or by doing something like x/(y+0.0001). – Erwin Kalvelagen Oct 16 '19 at 14:15
  • I will try x/(y+0.0001) hopefully not change my problem. and I have very complicate case than x/y –  Oct 16 '19 at 14:19