[ot-users] constraint error FORM

regis lebrun regis_anne.lebrun_dutfoy at yahoo.fr
Tue Mar 14 17:48:02 CET 2017


Hi Anita,

You are right, the constraint error is an obsolute error on the constraint. It is equal to |f(x_opt) - s| = |f(T(u_opt)) - s| where f is your code, T the inverse iso-probabilistic transformation that maps the standard space into the physical space, u_opt the design point (so in the standard space) and x_opt = T(u_opt) its image in the physical space.

Are you 100% sure that you compute f at the correct point in your verification? If you compare f(u_opt) with s, it is wrong (and I suspect that you did it ;-)). Otherwise there is a bug and we need more input from your side in order to catch it.

Cheers

Régis



________________________________
De : Anita Laera <anita.laera87 at gmail.com>
À : users at openturns.org 
Envoyé le : Mardi 14 mars 2017 15h25
Objet : [ot-users] constraint error FORM



Hi all,
I have a simple question regarding the constraint error of a FORM analysis, the constraint error is defined as |f(u_n) - s| , i.e. the absolute difference between the result and the threshold.

In my case, the result in the design point is 845.307471892986 and the threshold is 850 (in the physical space).
I would expect the constraint error to be about 4.69, but the value obtained with the method getConstraintError() is 4.59. Why?

If I calculate the difference between the result and the threshold for each performed evaluation, I never find 4.59.

Could it be different because it is calculated in the standard space u? How could I verify the value?

Thank you for your time!
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