Due to COVID 19 pandemic this year Direct PhD selection only consisted of an online interview.
A mail was sent by the authorities regarding the shortlist about 10 days before the interview. My interview was scheduled on 23rd of July. They had previously asked us to select 2 favourite subjects from the list of Gate topics on which they could interview upon. They had also asked for Statement of Purpose of the research work.
Subjects selected: Operating Systems and Database Systems.
On the day of interview a professor called me half an hour prior to the interview and asked me to connect as soon as they allow. There were total of 9 professors for the interview, but only 4 professors asked the questions.
Prof 1: Give a brief introduction about yourself and your academic background.
Prof 2: The topic you selected for research does not match with your favourite subjects. Why so?
Prof 3: What is concurrency in Operating Systems?
Prof 3: Why do we need concurrency?
Prof 3: Give any applications where you have found concurrency necessary?
Prof 3: Which operations need concurrency
Me: Answered (with respect to Read/Write Conflicts)
Prof 3: What is race around condition? How do we ensure it any protocol/algorithm?
Me: Explained. Specified Peterson’s Algorithm. Prof 3 told to write the code to implement Peterson algorithm
Prof 3: Any disadvantages of Peterson Algorithm? How can we overcome it?
Me: Answered. Explained about Baker’s Algorithm
Prof 3: Ok last question You know what atomic operation mean? Can atomic operations be practically implementable?
Me: Answered (Not sure though)
Prof 4: What are transactions? What difference you notice in maintaining concurrency in OS and concurrency in Database Systems.
Me: Defined and Explained.
Prof 4: What is consistency in ACID properties. Give a formal definition.
Prof 4: I give you 2 operation Fetch and Add & Compare and Swap operations. Both are atomic.Which one will you choose for synchronization and why so?
Prof 4: Gave 2 transactions with variables X, Y and asked the difference between serial and serializable schedule. Can the given transaction be serializable. If so how and if not why?
Prof 4: What protocols could you use to ensure concurrency in transactions.
Me: Locking Protocols (2 Phase Locking)
Prof 4: 2 Phase Locking can be applied to transactions I gave before. Can you brief out the proof that 2 PL ensures serializability.
Me: Answered whatever I knew. I did not remember the proof exactly but Sir was satisfied.
Prof 1: Write a program to find number of trailing zeroes ( Expected mostly in C)
Prof 1: Your program should be written with function
Prof 1: How will you modify it if instead of n I ask you for n factorial.
Prof 5: Your interests are in Cryptography. Tell me about the final year project.
Me: Answered partially. Sir wanted me to tell regarding the security parameters chosen to prove our model is secure.
Prof 5: Can you just prove formally empty set is a subset of every set.
Me: Gave an intuitive way. But was not satisfied.
Prof 1: You can leave.
The interview was nearly for an hour. The professors were expertized, kind and cooperative. The professors made the interview comfortable. It was a great interview experience from the professors of top most Institute in India.