(student) interview questions - programming for a robotics lab

Question

Hi all,

my robotics lab is looking for programmers to work on some projects we have at the moment.

We nailed down the requirements (mainly, c++ and experience with openGL and 3D), but due to obvious money constraints we can't afford to hire Great Developers. Instead we're going to settle for Talented Students, offering them projects for their dissertation/thesis and hoping for some fresh ideas and creativity from their side. We can also afford to pay students that just graduated (first job experience).

So my question is:

In your experience, how did you spot a Talented Student (computer scientist or engineer)? What questions did you ask? What else did help you in finding a candidate that turned out to be a Good Programmer? (note: they might not know much about a specific language, but might have the ability to learn pretty fast)

or, if you were the interviewee,

Which questions were asked that made you jump on the bandwagon? Or, if you had an awful experience, what - in retrospect - was an obvious warning signal that you ignored?

Please note that I am not looking for an argumentative answer. We can talk all day long about what's best for us and never agree.

Instead, I'm looking for tales from your experience. Anecdotes, stories, hints, everything will help.

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Background:

A bit more background: working for academia here is slightly different than working for the private sector (here = Italy). There are no 'deadlines' to 'sell' a product; instead, it's all proof-of-concept based. Nothing you start working on has the guarantee to be functional.

A comic best describes it: reinventing the wheel

I am considering doing Coding Questions for their interview, but all my colleagues are scoffing at me (too scary, nobody will ever come to work for us again, nobody really know how to code, etc).

Coding-wise, programming done by researchers is ... ugly. I am fighting to get a version control system in constant use, people have to be chased down to report bugs and document their code, everything is coded-so-that-it-works and rarely we go back to old code to 'fix bugs'. Basically once it's somewhat working, the project is closed and people go work on another project.

Lots has been reinvented and rewritten over and over again (just because nobody knew it was already there). People come and go, future is uncertain, but we play with robots so it's very cool :)

Furthermore, being really understaffed, nobody can follow you and guide you in your project. At best you're the one that has to come up with a plan, background literature and a working prototype.

Hence, we are looking for people that:

• have some background to get started
• can be highly independent
• do want to learn and build their own expertise in new fields

Answer 1

Firstly, in industry, coding questions are very much the norm - I'd be worried if coding questions weren't asked!

I've been responsible for doing technical interviews for about ten years now. And yes, I ask coding questions. But the questions themselves aren't really the point. What I'm more interested in is getting an idea of whether the candidate can think, and articulate their thoughts.

One question I ask (asuming the simple earlier stuff has gone well) is about inheritance heirachies. There is no one right answer, although there are a lot of wrong ones. But what's important is how they approach the question, the points they come up with in favour of one design over another.

Background knowledge is useful, in that it shows that they have an interest in the area in which you're working - but really knowledge can be gained. Intelligence is much more important.

However it's quite possible to have intelligent people who are impossible to work with! I haven't figured out how to determine who they are.

Answer 2

I have done such a project when I was a student: ie a 4-months project, working half-time. It was not about robots, per se.

I think that the most obvious requirement is motivation/passion. Since they'll be mostly on their own you will need them to be somewhat independent and able to think for themselves, this requires motivation first and foremost.

In order to determine whether the candidate is motivated or not, begin by asking them about the project itself. If they only gave it a cursory glance, they're likely not motivated. Also look at their experience / courses: optional courses in CS, projects they've done, etc... anything indicating that they really care about CS / development in general and are not there just because they've heard it paid well.

Then comes the question of ability. Like you said it might not be easy to spot those who will be smart enough to figure stuff out by themselves and DO things. Once again, you can ask them about past projects, having them detail the issues they faced and how they solved it.

Finally, I agree with you that some demonstration of their abilities is in order. They might be a bit tense initially, so I would do this at the end, once the interview is already going, you might have had a chance to get them to relax with the previous questions this way.

You don't necessarily need them to do coding questions, I think it's most about reasoning. Try to pick problems related to your area work, for example one you really had in the past, and get them to analyze the problem. If possible they should take the lead and ask you questions about the problem itself here.

We've had an issue with the robot not being able to analyze the images the camera took, it could not correctly determine the moving objects itself, do you have an idea how you would do that ?

Then you'll need to get them to think about a solution. You need a whiteboard here, and ask them to think aloud so that you can follow their reflexion. You'll probably need to nudge them a bit from time to time to keep them on track, their reaction to your input is also a key-point here, since you want them to be able to accept criticism and build on it, otherwise you might have issues directing them afterward.

Frankly, try to avoid asking them for the quicksort algorithm, or the introsort, or the radix sort... If they need sorting, they'll just fire up their computer and browse the internet. On the other hand, getting them to analyze an existing algorithm unknown to them (for example, the median of 5 sort) and checking that they understand why it works, could be worth it. If they need to work on their own, they'll need to be able to learn on their own too :)

Answer 3

As others say, try to hire someone that's motivated!

For master thesis students I put more emphasis on knowing the basic skills (programming, knowing how to use version control) as they don't stay on long enough to learn everything along the way.

If they're going to work mostly on their own and you have no special requirements on language I wouldn't focus much on language questions. But every decent programmer knows at least one language fairly well, get a sample or their prior work or make them code some simple application to test that they don't suck.

I'd focus more on algorithm and data structures. Ask rudimentary stuff that every programmer should know - when to use a list and when to use a vector, why summing a row-major matrix by iterating over the columns first is bad, basic complexity analysis questions, etc. That will sort out many of the bad weeds.

Ask some design questions too perhaps, e.g. what is "coupling" and why is it bad, ask them if they know what a design pattern is, etc.

Check that the applicants have a solid grasp of linear algebra and coordinate system changes in particular if they're going to work with any 3D stuff like OpenGL. In my experience, learning the API is simple, wrapping your head around how the transformations work less so.

Obviously, if you except them to perform any real robotics-specific you should check for that knowledge as well. E.g. estimation (understanding simple EKF and particle filters is a requirement in my book), control theory, pattern recognition, machine learning, vision, or whatever is useful for the particular task.

If I were hiring someone for theoretical work I would perhaps loosen up on the CS/programming skills and focus more on math knowledge. Someone with solid math skills will pick up the CS easily, and programming is just programming.

Ask for references or to see some of the prior work. Many great students already have some interesting project to show after graduation.

Answer 4

Actually, here's my best advice:

Recruit among your students.

Since you work for an academic institution I assume that either you or your colleagues teach. This provides you with a wealth of information about what potential recruits are capable of -- how fast they learn, how motivated they are, what they are good and bad at, how the code they turn in for the lab assignments and projects look like, etc.

Answer 5

I'm not sure how common this is at universities in general, but I would look for a games programming (or robotics) course on the transcript where the candidate, as a student, succeeded in completing a project with a team. It would ask the candidate to describe how that project worked (important technical details) and the role he had in the team. The only way to really tell if someone is good at something is to see what happens when they try it, and since you're in academia, recruiting students, that should not be a problem.