# [Ipopt] Problems about derivative checker and iteration

lqc234 lqc234 at 126.com
Wed Feb 24 00:39:24 EST 2010

```Hi everybody:
I have had a problem during using the Ipopt-3.6.1.And I have no idea about this problem for several days,I think that you might not think of this situation .
Suppose f(x)= x^2+2*x+1/x+3*x+4*x^3. This formula is very simple,however consider this situation: in my application,for example,1/x+3*x+4*x^3 is a very complicated part that I can't write this part of formula directly,in other words I must use some codes to describe this part,for example
a set of "for" cycle codes with complicated processing. Now I thought there are two problem.
First , the direvative checker tools can't deal with this situation because the complicated part 1/x+3*x+4*x^3 is not described directly.
The second problem is not easily to describe somewhat.
The variable x changes in every iteration,while I can't write 1/x+3*x+4*x^3 directly.So in every iteration I have to describe the  1/x+3*x+4*x^3 part using some codes every time .However, I found that the excution sequence is "eval_jac_g,eval_grad_f,eval_g,eval_f,eval_h" sometime,sometimes it is not this sequence.Now I don't know which part I should write these codes in,it should be in the eval_f? or eval_g? or in eval_grad_f?eval_jac?eval_h?.
I don't know the processing procedure during one iteration in Ipopt,those codes should used only once,I can't used those codes in eval_f ,eval_g,eval_grad_f,eval_jac_g,eval_h all.
I don't know if I have described the problem clearly.I hope so.
Anyone can give some suggestion?Thank you very much in advance.

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