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MIP constraint with sum of decision variables having certain value : $\sum_{i=1}^nx_i = 2 \implies \delta = 1$
I want to formulate a MIP constraint such that :
$$\sum_{i=1}^nx_i = 2 \implies \delta = 1$$$x_i, \delta \in \{0, 1\}$.
My problem is that delta should be one when this sum is exactly 2 and not greater or less than.
