# How to linearise max min constraints for multiple terms?

 0 Say, min{a_1...a_m} < max{b_1...b_m} asked 21 Jul '17, 07:34 Sulivan Cheung 11●3 accept rate: 0%

 2 I assume the $$a_i$$ and $$b_i$$ are variables. First, strict inequalities are anathema in optimization models. You need either to switch to a weak inequality ($$\min\{a_1,\dots,a_m\}\le \max\{b_1,\dots,b_m\}$$) or else specify a minimum acceptable difference ($$\min\{a_1,\dots,a_m\}\le \max\{b_1,\dots,b_m\}-\epsilon$$ for some $$\epsilon > 0$$). Second, I don't think there is any way to linearize this without introducing binary variables. What you are saying equates to $$a_i \le b_j$$ for some $$i$$ and $$j$$. You can introduce binary variables $$x_{ij},\,1\le i,j\le m$$, constraints $$a_i\le b_j + M(1-x_{ij})\,\forall i,j$$ and one more constraint $$\sum_{i=1}^m \sum_{j=1}^m x_{ij} \ge 1$$, where $$M$$ is some sufficiently large positive constant. answered 21 Jul '17, 10:58 Paul Rubin ♦♦ 14.6k●5●13 accept rate: 19%
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