Re: [Help-glpk] Can't read CPLEX file

[Andrew Makhorin]

> I currently have GLPK 4.9 installed and the following CPLEX file:
> maximize 1
> st
> - 2 x1 - 3 x2 <= -1
> 2 x1 + 3 x2 <= 1
> - 1 x1 - 1 x2 <= -4
> 1 x1 + 1 x2 <= 4
> bounds
> x1 free
> x2 free
> end
> 
> Cplex can read it.
> glpsolve:
> $ glpsol --cpxlp test.lp
> lpx_read_cpxlp: reading problem data from `test.lp'...
> test.lp:2: missing variable name
> CPLEX LP file processing error
> 
> 
> Why?

Because there is a syntax error in maximize statement. Note that
glpk does not support some features allowed in recent versions of
cplex format, in particular, constant terms in the objective.
For details about compatibility please consult the glpk reference
manual (Appendix C "CPLEX LP Format", pp.79-84).

If you need only a feasible solution, simply specify any variable
as the objective, for example:

   maximize x1