This is a misleading question.
You could break the poll down into modules or sections of the code and see how many people had understood every line of each section. No one person need to have looked over/understood every line as long as many people had understood each piece ... unless there was a way to slip something in the cracks.
I see your point and I was kind of expecting a response of this shade. I thought of including several choices, but then I would have to dilute this poll with subjective options like "No. But I have understood most of it" and "No. I have read most of it but only understood a small portion" and "I got the gist of the source files but none of the headers". Or a whole bunch of options for different sections of code and one for those who do not know any C++. Alright, so maybe this would be the better way to go, but that's not what's important. I mostly started this thread to hear from those rare savants who can wrap their minds around the entirety of a program. Guys who are real geniuses like Satoshi Nakamoto must be. So far the closest I've heard was Gavin Andresen in "Making Money" saying "I'm a geek, I understand this stuff".