PySAM vs SAM

Hello,
I have been using PySAM as a wrapper to make calls to the SAM simulation core compute modules. I model my solar panel performance through the GUI application and compared it with the PySAM output. I noticed that it wasn't exactly the same but was relatively close. I took a look at PySAM's documentation and under "Possible Problems" it says that I have tp provide my own calculations as PySAM doesn't handle it like the GUI application. Diving into the C++ code on GitHub, I located the areas where calculations are being made. My question is that if PySAM is a wrapper to the SAM simulation core model, when I call the execute() in PySAM does it make the call to the C++ library? If so all calculations done within the execute() function in the C++ library should be done when I call it through my python call? or why would my outputs differ? 

For some reference, I am using the Detailed PV Model - Residential Owner and I call the execute function on the pvsamv1.execute().

Thank you,
Fernando Estevez 

Hi Paul,

Thank you for a quick response, that makes sense. I went ahead and generated a set of SSC inputs from the SAM user interface to use it to cross reference my PySAM code. I noticed some variables such as spe_area, 6par_aisc, 6par_bvoc, cec_area, cec_i_mp_ref, etc, that I do not updated on my PySAM code. Are these variables that the SAM GUI automatically calculates and updates? When I was looking through the documentation for the SystemDesign Group it states that "This variable may need to be updated if the values of the following have changed".

Thank you,
Fernando Estevez