CO 350 Linear Optimization (Spring 2009)
TA’s comments for Assignment 2
Q1, Q2:
Most students got close but not many received full marks. A few common errors:
•
Not moving all constants in a constraint to the right hand side (e.g.

(4

2
x
3
)

x
2
≤ 
1).
•
Not including nonnegativity constraints. For example, in Q2, although it’s blatantly clear that
x
3
can only take positive values, it is still required to include
x
3
≥
0 to make it standard inequality
form.
•
Forgetting to ﬂip the sign of the RHS when reversing the sign of a constraint (e.g. turning
x
1
+
x
2
≥
1 into

x
1

x
2
≤
1).
•
In Q2, quite a few students took the constraint
x
2
≥
0 as a “real” constraint, and treated
x
2
as
a free variable. They substituted
x
2
=
u
2

v
2
and ended up capturing
x
2
≥
0 by

u
2
+
v
2
≤
0
,u
2
≥
0
,v
2
≥
0. While this is not “wrong”, it’s unnecessary and ineﬃcient in practice.
Q3:
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '07
 S.Furino,B.Guenin
 Optimization, TA, Mathematical optimization, Constraint, Candidate solution, Basic Feasible Solutions

Click to edit the document details