Originally posted by: HuuHuy

Dear all

I use Mixed integer Linear programming to solve RCPSP and I take example from LIBPSP with 30, 60, 90 and 120 tasks. For 30, 60 tasks, it took my computer under 1 second to get optimal solution; about 90 tasks : 4 seconds. Howerver , 120 tasks , it took my computer 2 days without solution. I give you some statistic of 12 tasks:

    Constraint : 3210
    Variables:    81497
        Binary      81374
        Integer        123

 Can you tell me the reason and how to fix this problem. I give you my MILP_Cplex model.( Please find my attachment)

Thank you

Le huu Huy

Hi,

have you tried to use CPO ?

http://fr.slideshare.net/mobile/PhilippeLaborie/euro2009

regards

Originally posted by: HuuHuy

Dear @AlexFleischer a1d4492b-6cf8-402d-ae3c-dd656c427dc7

I used CPO already. But I would like to run by MILP. Can you help me ?

Thanks

Huu Huy

Hi,

I tried

oplrun "TEST 120 tasks.mod"

with CPLEX 12.6.3 and I see

   Node  Left     Objective  IInf  Best Integer    Best Bound    ItCnt     Gap

*     0+    0                          161.0000       90.2345            43.95%
      0     0       90.2450   615      161.0000       90.2450    57647   43.95%
*     0+    0                          144.0000       90.2450            37.33%
      0     0       91.0000   477      144.0000     Cuts: 126    59207   36.15%
      0     0       91.0000   634      144.0000     Cuts: 322    63456   36.15%
      0     0       91.0000   568      144.0000     Cuts: 104    65220   36.15%
      0     0       91.0000   645      144.0000     Cuts: 384    72204   36.15%

after a few seconds

Regards