LpSum vs LpAffineExpression

[Tom van der Hoeven]

Hi,

in the following example:
---------------
from pulp import *
AA = LpVariable('aa')
BB = LpVariable('bb')
equationlist = [ (AA,1),(BB,2),(AA,5)]
print 'aff ', LpAffineExpression(equationlist)
print 'Lpsum', lpSum(coef*var for var,coef in equationlist)
---------------------------

the output is

__________________
aff 5*aa + 2*bb
Lpsum 6*aa + 2*bb
-------------------------

what happens is that AA is referenced twice.
This happened to me in a larger application.

Is a multiple reference to one variable forbidden for LpAffineExpression
or is it an error.

Tom

[Stuart Mitchell]

yeah that is a downfall of LpAffineExpression it assumes that you have already collected all the terms together

Stu

Tom

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Stuart Mitchell

PhD Engineering Science

Extraordinary Freelance Programmer and Optimisation Guru

www.stuartmitchell.com