I started to think there was something wrong with my model but that makes perfect sense since i know the values of each side of the constraint :)
Thank you so much for the answer! On Mon, Apr 16, 2012 at 1:09 AM, Andrew Makhorin <[email protected]> wrote: > > First of all, excuse my bad english. Im new at mathprog and trying to > > model some problem i get as output some strange thing: > > > > No. Row name Activity Lower bound Upper bound > > ------ ------------ ------------- ------------- ------------- > > ..... > > ..... > > > > 7 constraint[1] > > 0 -0 > > 8 constraint[2] > > 0 -0 > > 9 constraint[3] > > -3 -0 > > 10 constraint[4] > > -2 -0 > > > > I dont get why those values happen at this constraint, because neither > > of the variables or values are negative in the first place. The > > constraint is defined as follow: > > > > s.t. constraint{j in 1..n}: sum{i in 1..m} d[i,j] <= m * y[j]; > > > > Where m is a param defined in the data, positive integer, y is a > > binary variable and d[i,j] are real variables between 0 and 1 > > (0<=d<=1) > > > > Any help would be greatly appreciated!! thanks in advance > > By definition (in MathProg) the auxiliary variable for a row > (constraint) is always the difference between left-hand and right-hand > linear forms of the constraint. Thus, in your case > > constraint[j] = sum{i in 1..m} d[i,j] - m * y[j] <= 0. > > Since the solution found is primal feasible, in the row section you see > non-positive values (activities) of auxiliary variables 'constraint[j]'. > For more details please see the MathProg language reference, Subsection > 4.4 "Constraint statement". > >
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