In PulP modeling, I have an integer variable s that can take on values 0, 1, or 2. I want a binary indicator variable y such that y=1 if s=0 or s=2, and y=0 if s=1. I tried defining three binary variables z1, z2, and y, and setting up these constraints: z1 <= s <= 2 * z1 2z2 <= s s < 2z2 + 2 y = z1 * (1 - z2) Essentially, z1=1 means s>0, and z2=0 means s<2. Hence y=1 means s=1, and y=0 means s=0 or 2. However, this makes y non-linear, since it is a product of 2 variables. Is there a way to define y using only linear constraints? Continue reading...
