[Scip] problems with SCIPfree / SCIPreleaseCons

[Stefan Heinz]

Hi,

the answer is: It depends. Did you check the following explanation for  
capturing and releasing

http://scip.zib.de/doc/html/OBJ.html

After you created a constraint or a variable the objects have are 
captured. The simple reason for that is, if these objects are not 
captured they would get deleted right away. The capture which is added 
during creation is the one the user has to worry about. If you store the 
constraints and variables internally you do at that moment of creation 
usually nothing except adding these things to the SCIP problem. During 
the adding process another capture is put on the objects. For these 
capture you as a user do not need to worry about. These are internal 
SCIP captures. In the end when you are deleting you data structure you 
need to call the release function to remove the capture which was 
created during the creation of the objects.

Hope that clear that issue a little bit.

On 03/06/2012 05:05 PM, Hélène Toussaint wrote:
> Hi,
>
> I have a BCP code with one pricer and one constraint handler. I keep 
> in memory all the variables (included the variables generated by the 
> pricer) and all the initial constraints. I use several vectors like it 
> is done in the queens example. The constraints generated by the 
> constraints handler are not kept in memory. The initial constraints 
> are changed when I generate a new variable.
>
> I'd like to release all variables and constraints and free SCIP in the 
> same way it is done in the queens example but it causes assertions:
>
> If I call these functions :
>
> SCIPreleaseVar
>
> SCIPreleaseCons
>
> SCIPfree
>
> I have the following message caused by SCIPreleaseCons:
>
> src/scip/cons.c:4933: SCIPconsRelease: Assertion `!(*cons)->active || 
> (*cons)->updatedeactivate' failed.
>
This looks like that you called the release function to often. That has 
the effect that you remove a capture count which is made internally by 
SCIP which results into the deletion of the objected since the count 
reaches zero. The assert() check if the constraint in not active which 
should not be the case if it gets deleted.
> If I don't call SCIPreleaseCons the SCIPfree function asserts:
>
> src/scip/var.c:2842: SCIPvarAddLocks: Assertion `var != ((void *)0)' 
> failed.
>
I'am not really sure what forces this assert(). If the above stuff does 
not help send as the back trace such that we see the function call order.


> I have tried to run with valgrind (with the flag --leak-check=full) 
> but it did not give me useful information.
>
That does not help to find the issue :-(

Best Stefan
> I don't understand why I get these assertions. Do you have an idea?
>
> Best,
>
> Hélène
>
>
>
>
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