[Dip] Differences between GAP examples

[Florian Fontan]

Dear Dip community,

I am trying to get familiar with Dip and understand how it works. Could 
someone tell me the differences between the multiple DecompApp 
implementation examples for the Generalized Assignment Problem?
https://github.com/coin-or/Dip/tree/master/Dip/examples/GAP

For example, in GAP_DecompApp.cpp, I noticed that the setModelRelax call 
passes NULL as first argument:

     setModelRelax(NULL, modelName, i);

whereas in GAP_DecompApp3.cpp, an other model is defined:

     status = createModelPartKP(modelRelax, i);
     modelName = "KP" + UtilIntToStr(i);
     setModelRelax(modelRelax, modelName, i);

What does that mean? I haven't found any documentation about it

Florian