[SCIP] branch-and-price-and-cut

[Horváth Markó]

Hi Gerald,

ohh, okay. I combined this with callback scip_initlp and as I see, it is 
woking! Thanks!

(The 'initial' keyword confused me, because I thought, the initial LP is 
the very first LP, and not the first LP of the node...)

Thanks again! Best regards,
Marko

2022. 06. 20. 10:24 keltezéssel, Gerald Gamrath írta:
> Hi Marko,
>
> you should just set the initial flag of the constraint to TRUE when 
> creating the constraint. If I remember correctly, it should then 
> automatically be added to the LP relaxation of nodes where it is valid.
>
> Best,
>
> Gerald
>
> On 6/20/22 09:01, Horváth Markó wrote:
>> Hi,
>>
>> if I set it to TRUE, also nothing is happened. Should I use the 
>> callback scip_active for this purpose? Anyway, which is the best way 
>> to add new rows to the problem for branching purpose?
>>
>> Best regards,
>> Marko
>>
>> 2022. 06. 20. 8:44 keltezéssel, Gerald Gamrath írta:
>>> Hi Marko,
>>>
>>> about 2): did you set the constraints to initial?
>>>
>>> Best,
>>>
>>> Gerald
>>>
>>> On 6/20/22 08:18, Horváth Markó wrote:
>>>> Dear all,
>>>>
>>>> none of my attempts were succesful. I have two further questions.
>>>>
>>>> 1) Is it possible to add new rows to the problem of the new child 
>>>> nodes during a branching? When using scip_execlp, I could add 
>>>> (stick) new constraints to the child nodes, but I cannot find 
>>>> similar functionality for new rows.
>>>>
>>>> 2) Assume I added new constraints to the child nodes during 
>>>> branching. When a node is focused, is it possible to add new rows 
>>>> to the problem (based on these constraints) before the first LP is 
>>>> solved? I tried to modify the LP inside callback scip_active, 
>>>> however, nothing happened.
>>>>
>>>> Best regards,
>>>> Marko
>>>>
>>>> 2022. 06. 13. 9:42 keltezéssel, Horváth Markó írta:
>>>>> Dear all,
>>>>>
>>>>> I'm working on a branch-and-price-and-cut approach. Actually, it 
>>>>> is a branch-and-price approach, where until now, branching 
>>>>> decisions were handled by variable fixing (i.e., variables were 
>>>>> fixed by the propagation callback of the corresponding constraint 
>>>>> handler). However, I want to improve this branching, that is, in 
>>>>> each child node I want to add multiple rows to the problem. Of 
>>>>> course, I need to store these decisions to take them into 
>>>>> consideration during variable pricing. (So, yet it is a 
>>>>> branch-and-price-and-cut approach, but cuts are not added by 
>>>>> separation procedure, but branching). I would like to ask, what is 
>>>>> the best way to do that? (My best guess, is that in a branching 
>>>>> rule I add the rows to the problem, and I also create a constraint 
>>>>> sticked to child nodes. The corresponding constraint handler do 
>>>>> nothing (may be propagation only), but could be used in variable 
>>>>> pricing).
>>>>>
>>>>> Thanks, and best regards,
>>>>> Marko
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Scip mailing list
>>>>> Scip at zib.de
>>>>> https://listserv.zib.de/mailman/listinfo/scip
>>>>
-- 
Markó HORVÁTH PhD,
research fellow
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