Originally posted by: felycite28

Hello  everyone ,

I have small difficulties to define objective function of my model on python. My obj,func is more complicated but can you teach me how can I do that on the objective function of following facility location problem; I checked the python library of IBM but could not find similar example which has the same type of objective function ; if it is so difficult to explain,you can give me a reference model from the library which will be consistent to my example?

Ttahnk you in advance

You can query/modify the objective using the objective interface. There are many examples documented there. If you still have issues after looking that over, please show us some code and explain why it's not working for you.

Originally posted by: felycite28

Hello Ryan ,

I was looking for that document , thanks . let me try and if it does not work  I will show the code I developed  to discuss.

Many thanks

Originally posted by: Lou19

Hello everyone,

i'm new in CPLEX and Ihave some difficulties to write the problem (attached). For the simple one I can but in this one I have functions in the objective and my X is a binary matrix which I defined as:

varnames.append("x-" + str(i) + "-" + str(j) ) with a Binary vartype, 

I dont know what to do next in order to define my problem :/ please little help! 

You cannot have functions in a CPLEX objective function. You will have to expand your functions so that you get one single linear or quadratic expression.

Originally posted by: Lou19

Thank you for your answer.

I'll try that then.

I am not sure whether it will work in our case but one option would be to do a "symbolic evaluation" of your function. That is, instead of sticking numbers or variables into X, you stick objects there that behave like numbers. Then you apply L to it by writing a short program that does that. This can avoid errors you would make by calculating things by hand.

Originally posted by: Lou19

I'm not sure I understand what you are suggesting.

If I replace my X with a symbol let say x1 x2 x3... the problem will be that for using the function L I will need all the matrix X.

Maybe I didntget your suggestion.

Thanks!

What I meant is something like this: http://www.scipy-lectures.org/advanced/sympy.html, in particular http://www.scipy-lectures.org/advanced/sympy.html#symbols.If you use symbol names that you can later easily translate into variables (like name 'x_0_1' to denote variable x[0][1]) then it should be pretty easy to read the linear expression from the final results.

The homepage of SymPi is http://www.sympy.org/en/index.html