Duplicate Column x4644 and x245 makes problem unbounded

[Casey]

I am running a problem and I get this error message along with several
from CPLEX stating the problem is infeasible or unbounded, failure to
solve MIP subproblem, no solution exists, no basis exists,
unrecoverable failure with no integer solutions, etc

starting from the top... what does duplicate column refer to?

At this point I am guessing I will start turning off or grossly
simplifying constraints until I find the one that is causing the
problem.

Does anyone know an easier way to do this?

Also is there a catalog somewhere of what the different error messages
refer to?

I would appreciate any insight...

thanks!

Casey

[Robert Fourer]

Casey,

To see which AMPL variables are numbered 4644 and 245 in the solver, use
"display _svarname[4644], _svarname[245];". Duplicate columns are ones that
have exactly the same coefficients, or at least exactly the same
coefficients in the constraints. In some cases, unboundedness of the
problem can be deduced immediately from the existence of duplicate columns.

There is extensive CPLEX documentation that includes explanations of error
messages. You should have received this documentation (probably in the form
of computer files) with your CPLEX software.

Bob Fourer
4...@ampl.com