how to add constraint in Pulp BinPacking such that two items are not assigned in same bag

Question

I'm using this code and want to add a constraint such that say item a and b are not assigned in the same bag

https://github.com/mbasilyan/binpacking/blob/master/binpacker.py?lipi=urn%3Ali%3Apage%3Ad_flagship3_pulse_read%3BVqIyMFQWR9epdBxSRfrU%2BA%3D%3D — Ankita Samariya, Feb 24 '18 at 20:28

score 3 · Answer 1 · answered Feb 24 '18 at 20:34

3

Let

x(i,j) = 1 if item i is placed in bin j
         0 otherwise

Then

x(a,j) + x(b,j) <= 1 for all j

will prevent a and b to be placed in the same bin.

answered Feb 24 '18 at 20:34

Erwin Kalvelagen

prob += lpSum([x["bread", i] + x["squash", i] for i in range(maxBins)]) < 1, ("Item Constraints -- " + str(j[0])) This is what i added. Doesn't work – Ankita Samariya Feb 24 '18 at 21:13
Indeed. That is something very different than what I suggested, So it should not work. – Erwin Kalvelagen Feb 24 '18 at 21:39
prob += lpSum([x["bread", i] + x["squash", i] for i in range(maxBins)]) <=1, ("Item Constraints -- " + str(j[0])) I did apply a "<=" as you suggested just accidentally posted wrong Is there any thing else that I should change? – Ankita Samariya Feb 24 '18 at 21:54

1 Answers1