[Scip] Early Branching issues

[Stefan Heinz]

Hi Jose,

On 02/07/2013 12:20 AM, Jose L Walteros wrote:
> Hi Stefan,
>
> Thanks for your quick response,  I changed the code as you suggested (I am
> also changing some other parameters and I guess I confused the TRUE
> parameter as the way to do it, thanks for the clarification) but still no
> additional cut are generated.
>
> I am using now:
>
> SCIP_CALL( SCIPsetSeparating(scip, SCIP_PARAMSETTING_AGGRESSIVE, TRUE) );
>
> I also tried the default.
>
> For this formulation all the constraints of the master problem are Set
> Partitioning constraints defined as:
>
> SCIP_CALL( SCIPcreateConsBasicSetpart(scip, &(conss[s][i]), name, 0, NULL)
> );
> SCIP_CALL( SCIPsetConsModifiable(scip, conss[s][i], TRUE) );
One think, if you stop generating new variables completely, you should 
change the "modifiable" flag of the constraints to FALSE. Additionally 
you could turn off your pricer(s) and force a restart. That would run 
presolving for example again. Check the method SCIPrestartSolve():

http://scip.zib.de/doc/html/scip_8h.shtml#a08e665c374c599f96c4968ce8cf108ba

I am not sure but the modifiable issue can be the/a reason for not 
executing the separation. Try it and if does not work, I will check the 
code (during the day tomorrow).

Best and good night Stefan
>
>
> I know  that no separators are called because in the execution summary the
> number of calls to all separators is zero.
>
> Is there anything I am missing?
>
> Thanks
>
> -Jose
>
>
>
>
>
>
> On Wed, Feb 6, 2013 at 5:53 PM, Stefan Heinz <heinz at zib.de> wrote:
>
>> Hi Jose,
>>
>> It should be possible to turn on the separation. The bool parameter you
>> changed from TRUE to FALSE has nothing to with turning on or off the "OFF"
>> mode.
>>
>> http://scip.zib.de/doc/html/**scip_8h.shtml#**
>> af91abf95639f1bf2022c11d13a032**b10<http://scip.zib.de/doc/html/scip_8h.shtml#af91abf95639f1bf2022c11d13a032b10>
>>
>> It does the parameter change "quite" or not. Meaning with or without an
>> output via the message handler. You need to change the second parameter to
>> one of the followings:
>>
>> * SCIP_PARAMSETTING_DEFAULT which are the default values of all separating
>> parameters
>>
>> * SCIP_PARAMSETTING_FAST such that the time spend for separating is
>> decreased
>>
>> * SCIP_PARAMSETTING_AGGRESSIVE such that the separating is done more
>> aggregative
>>
>> * SCIP_PARAMSETTING_OFF which turn off all separating
>>
>> Probably you want to try SCIP_PARAMSETTING_DEFAULT first.
>>
>> Best Stefan
>>
>>
>> On 02/06/2013 09:59 PM, Jose L Walteros wrote:
>>
>>> Hi all,
>>>
>>> I am solving a problem via Branch and Price. For one of my experiments, I
>>> am interested in stopping the pricing at a certain point in the B&B tree
>>> to
>>> heuristically obtain a good solution. Since I am no longer pricing new
>>> variables, I am wondering if it is possible to activate the separate
>>> algorithms to add default SCIP cutting planes after no more columns are
>>> generated.
>>>
>>> I tried to play with SCIP_CALL( SCIPsetSeparating(scip,
>>> SCIP_PARAMSETTING_OFF, TRUE) ); changing it from TRUE to FALSE but I did
>>> not get the expected beheavior.
>>>
>>> Tanks
>>>
>>> -Jose
>>>
>>>
>>>
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>>>
>>