[Dip] "Not a mixed-integer problem" message when using DIP with CPLEX

[Ted Ralphs]

We've seen messages like this with CPLEX for a long time in many
contexts (not just DIP). Unlike most other solvers, CPLEX makes a very
strong distinction between an LP and a MIP. Although conceptually, the
only difference is whether there exist variables that are marked as
integer type or not, CPLEX takes the "problem type," as set by the
user, as strongly dictating what can and cannot be done when
manipulating the model. CPLEX also erases all solution information
when switching problem type. The use of Cgl actually requires the
problem type to be switched back and forth and this causes problems. I
thought we had actually fixed all of these problems over time, so if
you are seeing this error now, it should be an indication of a true
problem.

Ted

On Wed, Jan 26, 2011 at 1:49 PM, Matthew Galati
<matthew.galati at gmail.com> wrote:
> I know about it.... it doesn't seem to effect anything - except that it is
> annoying.
>
> It is on my ToDo list to investigate why that message appears. I think it
> has something to do with the odd design of OsiCpx.
>
>
>
> On Wed, Jan 26, 2011 at 1:46 PM, kim <kim at hamilton-vejlin.dk> wrote:
>>
>> I just set up DIP to use CPLEX instead of CBC and it works well but I am
>> getting some odd messages at the beginning of the program run.
>>
>> As one of the first things I get a string of messages all saying:
>> "CPX0000  CPLEX Error  3003: Not a mixed-integer problem."
>>
>> This happens before the search is actually started and there is always
>> one "error 3003" for each block. It doesn't seem to have an effect at
>> all and the program behaves as expected, but it seems odd.
>>
>> Does anyone have in idea what those messages are about and if I should
>> see it as a sign I have not set up the DIP/CPLEX combination correctly?
>>
>> -Kim
>>
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-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted