ralna / CUTEst

The Constrained and Unconstrained Testing Environment with safe threads (CUTEst) for optimization software
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Inconsistencies in problem classification strings #46

Closed chrhansk closed 2 months ago

chrhansk commented 2 months ago

We were discussing the classification of the problems in the CUTest suite and found some inconsistencies specifically regarding how constraints are reported in the classification of nonlinear equation (NE) problems.

As an example, the JUDGENE problem is classified as NOR2-MN-2-20, i.e., having 20 constraints. This is reflected in the dimension obtained when instantiating the problem. Of course, these correspond to the residuals to be minimized.

Conversely, the HATFLDBNE problem is classified as NOR2-AN-4-0, i.e., having no constraints despite having a residual vector with 4 entries.

There are several other instances exhibiting these discrepancies (I wrote a script to detect these kinds of problems).

The question in this regard is which convention should be adopted (zero or the number of residuals, I would prefer the latter) and stick to that convention consistently.

nimgould commented 2 months ago

I am very happy to correct any mistakes you find (thank you). The second classification is a mistake, it should be 4-4. This is because we view the problems from an optimization perspective, the second number is the number of (non-simple-bound) constraints (inconsistent or otherwise), in this case the number of residuals.

chrhansk commented 2 months ago

I appreciate the quick feedback. If the number of constraints in the classification should coincide with the number of residuals (given by the number of constraints in the problem), then we have the following discrepancies:

There are some cases where the classification number of constraints is not zero, but another value entirely. This may (?) be due to the conversion of linear constraints into bounds in the original problems, which I think does not make sense for NE problems, but I could be mistaken...

nimgould commented 2 months ago

Thank you very much, I will update as soon as I get a free few hours.

nimgould commented 2 months ago

Updates now on https://bitbucket.org/optrove/sif/src/master/ Thanks, once again