Gregor Hendel

If this problem mentioned is resolved, I am happy to accept. I never really got to look at the restructured text documentation, so any improvements are appreciated.

Aren't we using the sort level anymore? We should...

Are you sure that the old CPLEX version is not available anymore? You can probably request it from IBM support. I am not surprised that Gurobi and Mosek are not...

I am also using Ubuntu 18.04. Unfortunately, I cannot really help on the above issues you are experiencing. SoPlex and SCIP evolve together, so it is not surprising to me...

Let's wait with that until I have finished the reduction index #21

Have you read the documentation of sortlevel? ``` sortlevel : level on which to base column sorting, '0' for group level, '1' for column level ```

The column headers consist of >= 1 levels, depending on attributes such as `indexsplit`. The sortlevel functionality should allow to specify the level of the column keys, by which the...

You are right, group level is too specific and has been generalized in the mean time (because multiple levels of group keys are possible).

Yes, there is a pandas function, (`sort_axis`, I guess). We are free to do whatever we want. I would suggest that it applies to both data frames, although the meaning...

There should be, IMHO, the possibilty not to sort, maybe by assigning `None` to the sortlevel (Note that this should be even the default behavior).