Re: [Help-glpk] problem with glp_ios_heur_sol

[Giorgio Sartor]

The difference is the preprocessing.
If the problem has, for example, x variables (say 192), it is possible that 
after preprocessing (activated with presolve) the problem has less than x 
variables (say 186). glp_ios_heur_sol would need 186 but you give him 192 
variables. That's why you had those problems with initial solutions.


- G. S. -

Il giorno 06/ago/2013, alle ore 13:13, Le Dinh Danh <address@hidden> ha scritto:

> Oh great! It works now. Thank you so much G.S. I try your way and it
> is correct now.
> However, I really don't know why. I thought that the default presolve
> in GLPK using simplex method and it should work the same as we call
> simplex solver (with parm.presolve = OFF).
> It takes me a lot of time. Thank you once again and good work!
> 
> On Tue, Aug 6, 2013 at 12:42 PM, Giorgio Sartor <address@hidden> wrote:
>> Ok. I really think that the problem is the presolve because I had the same 
>> problem months ago.
>> At least just try adding glp_simplex before glp_intopt and disable presolve.
>> Presolve is not default in GLPK.
>> 
>> 
>> - G. S. -
>> 
>> Il giorno 06/ago/2013, alle ore 12:31, Le Dinh Danh <address@hidden> ha 
>> scritto:
>> 
>>> Oh I forgot to tell you that I suppose to use the default presolve in
>>> GLPK and do not explicit use any other for it. I know that if I don't
>>> use the presolve default I have to use some presolve like simplex or
>>> so. So in my case  parm.presolve = ON is neccesary.
>>> For my heuristic solutions I am sure that  they are correct, because I
>>> can verify it manually myself.
>>> 
>>> On Tue, Aug 6, 2013 at 12:23 PM, Giorgio Sartor <address@hidden> wrote:
>>>> Well, I don't know what you mean exactly but setting parm.presolve = ON is
>>>> never NECESSARY! (It is necessary only if you don't want to use glp_simplex
>>>> before glp_intopt). If you don't use it, my suggestion is to use 
>>>> glp_simplex
>>>> before glp_intopt and disable parm.presolve. In this case, if the integer
>>>> solution found is incorrect means that the solution you pass is incorrect.
>>>> 
>>>> 
>>>> 2013/8/6 Le Dinh Danh <address@hidden>
>>>>> 
>>>>> Hi G.S,
>>>>> It is neccesary to set parm.presolve=ON before solving MIP. In fact, I've
>>>>> tried with parm.presolve=OFF but the results are always 0. Anyway, thank
>>>>> you.
>>>>> 
>>>>> 
>>>>> On Mon, Aug 5, 2013 at 5:34 PM, Giorgio Sartor <address@hidden> wrote:
>>>>>> 
>>>>>> Ok. Just try parm.presolve=OFF and let me know if then works.
>>>>>> 
>>>>>> 
>>>>>> - G. S. -
>>>>>> 
>>>>>> Il giorno 05/ago/2013, alle ore 16:51, Le Dinh Danh <address@hidden> ha
>>>>>> scritto:
>>>>>> 
>>>>>> Hi Giorgio Sartor,
>>>>>> 
>>>>>> On Mon, Aug 5, 2013 at 4:14 PM, Giorgio Sartor <address@hidden>
>>>>>> wrote:
>>>>>>> 
>>>>>>> Is glp_iocp.presolve activated?
>>>>>> 
>>>>>> Yes, I have already set parm.presolve = ON.
>>>>>>> 
>>>>>>> A common cause of incorrect solutions is that your solution is correct
>>>>>>> for the original problem but not correct for the current problem (which
>>>>>>> could have been modified by GLPK during the solving process).
>>>>>>> Stupid question: does your solution start from position 1 of the array?
>>>>>> 
>>>>>> Yes, of course.
>>>>>>> 
>>>>>>> 
>>>>>>> - G. S. -
>>>>>>> 
>>>>>>> Il giorno 05/ago/2013, alle ore 14:58, Le Dinh Danh <address@hidden>
>>>>>>> ha scritto:
>>>>>>> 
>>>>>>> With "the result is still incorrect" I mean after calling the callback
>>>>>>> function, the solver find the solution but it is not correct one. I 
>>>>>>> don't
>>>>>>> know why. If I don't call the cacllback, the solve provide a good 
>>>>>>> solution.
>>>>>>> I can check it manually.
>>>>>>> 
>>>>>>> 
>>>>>>> On Mon, Aug 5, 2013 at 1:19 PM, Giorgio Sartor <address@hidden>
>>>>>>> wrote:
>>>>>>>> 
>>>>>>>> What do you mean with "the result is still incorrect"?
>>>>>>>> 
>>>>>>>> 
>>>>>>>> - G. S. -
>>>>>>>> 
>>>>>>>> Il giorno 05/ago/2013, alle ore 12:57, Le Dinh Danh <address@hidden>
>>>>>>>> ha scritto:
>>>>>>>> 
>>>>>>>>> the result is still incorrect.
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> --
>>>>>>> Le Dinh Danh
>>>>>>> LIRMM, 161 rue Ada, 34095 Montpellier Cedex 5
>>>>>>> Email: address@hidden; address@hidden
>>>>>>> Tel: (+84) 912.449.666; (+33) 6.52.98.59.66
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> --
>>>>>> Le Dinh Danh
>>>>>> LIRMM, 161 rue Ada, 34095 Montpellier Cedex 5
>>>>>> Email: address@hidden; address@hidden
>>>>>> Tel: (+84) 912.449.666; (+33) 6.52.98.59.66
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> Le Dinh Danh
>>>>> LIRMM, 161 rue Ada, 34095 Montpellier Cedex 5
>>>>> Email: address@hidden; address@hidden
>>>>> Tel: (+84) 912.449.666; (+33) 6.52.98.59.66
>>> 
>>> 
>>> 
>>> --
>>> Le Dinh Danh
>>> LIRMM, 161 rue Ada, 34095 Montpellier Cedex 5
>>> Email: address@hidden; address@hidden
>>> Tel: (+84) 912.449.666; (+33) 6.52.98.59.66
> 
> 
> 
> -- 
> Le Dinh Danh
> LIRMM, 161 rue Ada, 34095 Montpellier Cedex 5
> Email: address@hidden; address@hidden
> Tel: (+84) 912.449.666; (+33) 6.52.98.59.66