How to express this logic ?

[Zhongjie Guo]

Dear,

      I have an optimization problem in which there is a logical operation:

      A = 1, if Q>0; A = 0, if Q=0.

      where Q is a continuous variable great than or equal to 0.      A is a binary variable.

      Does any friend know how to expression this logical operation in Yalmip+cplex?

      thx

[Johan Löfberg]

That is practically impossible to implement as solvers work with numerical tolerances, and thus cannot work with strict inequalities, and 0 and 1e-10 and -1e-10 etc are essentially the same numbers.

the closest big-M model you can do is variants of [-epsilon + Q <= M*A, epsilon-Q <= M*(1-A)]

[Zhongjie Guo]

Alright.

Thank you  all the same :)