[SCIP] Question about "type" of MIPLIB instances

[Gregor Hendel]

Hi Tony,

the type classification uses the constraints statistics of the problem 
after presolving of the final run, e.g., after the last restart. The 
most likely explanation is that conflict analysis created bound 
disjunction constraints, which are not linearly representable. If this 
happens during the first run, and then SCIP performs a restart, such 
constraints become a permanent part of the problem, and the type 
classification says "CIP", which is the most general problem class it 
knows. You can find the type classification code in check/check.awk.

The statistics may look as follows:

Constraints        :     Number  MaxNumber  #Separate #Propagate    #EnfoLP    #EnfoRelax  #EnfoPS    #Check   #ResProp    Cutoffs    DomReds       Cuts    Applied      Conss   Children

   benderslp        :          0          0          0          0          2          0          0         18          0          0          0          0          0          0          0

   integral         :          0          0          0          0          2          0          0         18          0          0          0          0          0          0          4

   varbound         :         93         93         12       1257          0          0          0          0          0          0          0          0          0          0          0

   setppc           :         37         37         35       4937          0          0          0         11          8          2          0          0          0          0          0

   linear           :        655        655         35       4940          0          0          0          5         34         56         40          0          0          0          0

   orbitope         :          1          1          0       3989          0          0          0          4          0          0          0          0          0          0          0

   logicor          :          5          5         35         77          0          0          0          0          0          0          0          0          0          0          0

   bounddisjunction :          2          2          0        177          0          0          0          0          0          0          0          0          0          0          0

Besides bound disjunction constraints, the second explanation could be 
the extraction of auxiliary and constraints within the gate extraction 
presolver.

Best,
Gregor

Am 24.08.19 um 01:52 schrieb Wang, Tony Congqian:
>
> Hello community,
>
>
> I have used SCIP on the MIPLIB2017 benchmark set with make test. At 
> the end I noticed that some instances where classified as type "CIP" 
> although every Problem was obviously a MIP. Does this happen when 
> logic or constraints are used by scip? Does this actually make a 
> difference in how the programm works compared to the MIP instances?
>
>
> Best regards and many thanks,
>
> Tony
>
>
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