# [Ipopt] Problems about derivative checker and iteration

Stefan Vigerske stefan at math.hu-berlin.de
Wed Feb 24 04:31:21 EST 2010

```Hi,

you may use the new_x flag that Ipopt provides for all the eval_*
functions. That is, if new_x is set to true in any of these routines,
store these values in your TNLP object. As long as new_x is false, you
can use return this evaluated data in all eval_* functions.

Stefan

lqc234 wrote:
> 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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--
Stefan Vigerske
Humboldt University Berlin, Numerical Mathematics
http://www.math.hu-berlin.de/~stefan

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