Originally posted by: YassH

Hi,

Today I installed CPLEX on my MAC-OS such as I can use the CPLEX library.

I started with the function cplexlp and obviously it's not working.

Whatever I put as Inputs, I always get empty outputs "[]" for the basic variables and "-8" for the first slack variable.

Did I miss something during the installation??

I attached a screenshot to illustrate the problem.

Thank you in advance,

Best Regards

In the reference documentation for function cplexlp() you find this:

[x, fval, exitflag] = cplexlp(...)

So what you call x3 is in fact the exitflag. According to this page an exitflag of -8 means that your problem is infeasible or unbounded. That is why the x vector returned is empty and there is no objective function value to return. You should probably take a look at the examples that ship with CPLEX or at least check the reference documentation of the functions you are using.

Originally posted by: YassH

Thank you Daniel for your quick response.

Unfortunately, this problem is not unfeasible and I also tried with other LPs and it always gives me empty solutions and the exit flag -8.

It is not infeasible, but it is unbounded (and hence the dual is infeasible), isn't it?

Since you do not specify any lower bounds all variables can be set to -infinity, thus there is no finite optimum.

Originally posted by: YassH

Another LP.

Originally posted by: YassH

Thank you Daniel, It worked.

 I thought that the boundary was by default set to [0,Inf[.

Best Regards