Good software for linear/integer programming I never did any linear/integer programming so I am wondering the following two things


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*What are some efficient free linear programming solvers? 

*What are some efficient commercial linear programming solvers? 


It would be nice to supply a dummy usage example with each proposed answer.
Also what if wish to solve a integer programming problem? What are the answers to the above two questions in this case?
I know that integer LP is a hard problem but there are some relaxing methods that are sometimes employed in order to obtain a solution to an integer programming problem. Are there any software packages implementing this kind of stuff?

The Konrad-Zuse Institute in Berlin (ZIB), Germany provides a nice suite to solve all kinds of LP / ILP tasks. It includes:


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*zimpl: a language to model mathematical programms

*SCIP:  a mixed integer programming solver and constraint programming framework

*SoPlex:   a linear programming solver

*and more 


Best of all, it is free! And all implementations are reasonably fast. 
The state of the art in the commercial sector is probably IBM's CPLEX Studio. This is an expansive piece of software, but IBM has an academic program where you get free licenses. However it is a bit of a pain to apply. I used to work with the CPLEX package because it includes this nice modelling language ampl. However when the equivalent free zimpl came out, I switched to the more available ZIB package.
