MIT15_053S13_iprefguide

Xi xj 1 if item i is not selected then item j is not

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: If item i is selected, then item j is not selected. xi + xj : 1 If item i is not selected, then item j is not selected. -x i + x j : 0 At most one of items i, j, and k are selected. xi + xj + xk : 1 At most two of items i, j, and k are selected. xi + xj + xk : 2 Exactly one of items i, j, and k are selected. xi + xj + xk = 1 At least one of items i, j and k are selected. xi + xj + xk � 1 Table 2. Simple constraints involving two or three binary variables. Restricting a variable to take on one of several values. Suppose that we wanted to restrict x to be one of the elements {4, 8, 13}. This is accomplished as follows. x = 4 w1 + 8 w2 + 13 w 3 w 1 + w 2 + w 3 = 1 wi E {0, 1} for i = 1 to 4. If we wanted to restrict x to be one of the elements {0, 4, 8, 13}, it suffices to use the above formulation with the equality constraint changed to "w1 + w2 + w3 : 1." Section 4. Other logical constraints, and the big M method. Binary variables that are 1 when a constraint is satisfied. We next consider binary variables that are defined to be 1 if...
View Full Document

Ask a homework question - tutors are online