[Help-glpk] Knapsack problem using GLPK

[Lingzi Li]

I am using GLPKMEX to develop my project now. It is a branch-and-price 
problem, and I use GLPK to solve Lagrangian relaxation's master and sub 
problems. The subproblem is like the following:

min  y - sum(ui*xi)
s.t. sum(wi*xi) <= c*y
     xi + xj <= 1 (for some (i,j))
     xi, y are binary

(variables are xi and y)

When there are 80 variables, it takes 9 minutes to run out a solution. But if 
there are 100 variables, it will take more than 3 hours. And I do belive that 
most of the time is in subproblem mentioned above. Do you think it is normal 
for 100 variables to take that long time? Or do I need to do some special 
settings for large scale problem? But acturally I don't think 100 variables 
is "large" scale. Thank you very much in advance for your help!

----------------------------------------
This mail sent through www.mywaterloo.ca