NVIDIA interview questions

I first got 2 telephone interviews, which were not that difficult and mostly based on Computer Networks and OS. Then I was called onsite. I had 6 Interviews - 2 telephony, 1 lunch, 3 face to face. The onsite telephone interviews weren't clear and though the job description didn't mention Machine Learning and Compiler Construction I was asked questions about it.

I was addressed by a Headhunter whom I transferred my CV. Afterwards I had 2 phone interviews - one with a VP - the other one with one of the Sr. Directors. It was very difficult to schedule calls and in the end two times the contact person didn't "show up". I stepped back from this Opportunity and dropped further calls.