Send Help-glpk mailing list submissions to
address@hiddenTo subscribe or unsubscribe via the World Wide Web, visit
https://lists.gnu.org/mailman/listinfo/help-glpkor, via email, send a message with subject or body 'help' to
address@hiddenYou can reach the person
managing the list at
address@hiddenWhen replying, please edit your Subject line so it is more specific
than "Re: Contents of Help-glpk digest..."
Today's Topics:
1. Re: SOLVED : problem with glp_ios_heur_sol (Giorgio Sartor)
----------------------------------------------------------------------
Message: 1
Date: Tue, 6 Aug 2013 15:08:58 +0200
From: Giorgio Sartor <
address@hidden>
To: "
address@hidden" <
address@hidden>
Subject: Re: [Help-glpk] SOLVED : problem with glp_ios_heur_sol
Message-ID: <
address@hidden>
Content-Type: text/plain; charset=us-ascii
Just to clarify:
glp_simplex : LP solution
glp_iocp.presolve = ON : LP solution + preprocessing
- Gioker -
Il giorno 06/ago/2013, alle ore 14:55, Le Dinh Danh <
address@hidden> ha scritto:
> OK, I find it clearer now, Thank you so much for your help man. Good work!
>
> On Tue, Aug 6, 2013 at 2:35 PM, Giorgio Sartor <
address@hidden> wrote:
>> 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
>
>
>
> --
> 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
------------------------------
_______________________________________________
Help-glpk mailing list
address@hiddenhttps://lists.gnu.org/mailman/listinfo/help-glpkEnd of Help-glpk Digest, Vol 129, Issue 5
*****************************************