Interview

Just spent the whole day down in Hamilton for a job interview. Six others, all from the University of Auckland, travelled down. Took around one and a half hours each way. I wouldn't have been a pleasant journey if you didn't make sure your bladder was empty. If not, you'd be squirming to flush our your memory leak. Core dumps can be archived.

The first test was an IQ test which constisted mainly of words and number associations. Then there were different tests for people who were going for different positions: VHDL and software. For VHDL, the test was not timed. The software test, which I was originally given, came in three parts: Algorithms, Linux proficiency, and C code.

The algorithm part was not do-able at all.  I didn't understand the significance of the big O notation, space, and amortise of the functions we had to write:

• For a singly linked list a with an unknown number of elements n, write a function called get_n that takes in the list and a number k that returns the (n - k)th element from the list.
• For a singly linked list a, write a function called check_linked that checks for cycles in the linked list and returns true if there are or false if not.
• For an array a with a known number of elements n, write a function that rotates the list at element k.
• Something about having a list of page tables that can be written to by Applications and asking how we could make sure they weren't being used by other Applications requesting the pages being written to in an efficient way.
• A question that was too long for me to remember.  Something about managing a list of resources and figuring out the resource intensive ones.  They noted that going through the whole list would be too inefficient so they proposed a relaxed algorithm which had something to do with n bins and sets.
• A router can delay the transmission of packets.  There will be 24*60*60 = 86,400 different values for time.  Find a way to reduce the number of values below 1000.

The Linux proficiency test was hard as well.  It was a collection of short questions mainly about what commands should be used to get certain information and some administration questions.

The C test was a bit better but my brain wasn't holding up well enough.  Some of the questions were:

• What is wrong with this: x = x++;  ?
• Find the bug in the internet checksum code.  (Casting of addr inconsistently)
• In this source code, why is the assert always failing?  (Passing of a pointer and allocating memory to it and asserting that the pointer is no longer a null reference)
• Explain why the outputs are like this?  (int a[10] created and print outs of its size and each of its elements are made)
• What is another way to do the same: node_t->size ?
• What other ways are there to do a[2] without using the ++, += and comma operators?
• Write a recursive function that performs the factorial calculation.
• Complete the function for inserting an element into a linked list.

Well after those three tests, we were given a small tour of the office space by the Appliance person.  They seemed really bubbly and joyful but we were too brain dead to laugh with him.  We were pretty quiet.  So after killing a bit of time through more talking and asking of random questions, lunch was finally ready.  The company has a free lunch on Fridays so we got to join in.  The way they laid out the food, it was more like a "make your own sandwich" sort of thing. We were also made to sit amongst the other workers so we could another feel for the company. Alienating ourselves by us all sitting at the same table would have looked awkward.  The table I was at, there was an American guy who worked for AoL and some other small companies and he did some security work for the predecessor to CIA.  We ended up talking about different types of briberies and using buffer overflows for hacking.

So after lunch had finished, we got started with the interviewing process.  I was picked to go first and funny enough I didn't get too nervous.  Got asked a few questions about what specific part of a project I enjoyed at University and what paper I found most useful.  They went over the C test with me which I got 6/10 and I think they were pleased with it; especially the x = x++ question, thought they were debating as to whether my answer was "the" correct answer.  Then I got asked about the different types of storage class specifiers for variables; auto, extern, void, static, and register.  Somehow bashed my way through that with the help of "braces" to explain the scope and lifetime of the variables.  Then I got to ask my questions and the important one was:  How was it decided that certain candidates would be given the software test or the VHDL test?  The answer was, they considered our CV and the papers we took and decided which areas they felt we'd be best suited.  Additionally they were interviewing people for the Card software side rather than just Appliances so that cleared things up a bit.  But I did stress that I had expected to do the VHDL test rather than the software test since I expressed my interest in that area in the feedback form when the company came to University for an exhibition.  So after that realisation, I got to do the VHDL test and I ended up taking about one and a half hours to do it which wasn't very long considering the others took more than two hours each.

Some of the VHDL questions:

• Given this circuit, express it in VHDL.  How can you increase the clock frequency of this circuit?
• Find 3 syntax and 1 functional error in the following VHDL code.  Why will this VHDL code not be used when implementing on a Xilinx FPGA.
• What are the disadvantages to a logic element with 4 inputs to an LUT with a flip-flop at the output?
• What are the disadvantages of clocked memory resources?
• What is the metastability problem?  How can you make a circuit more tolerant of metastable signals?
• Draw the output for the clock selector circuit.  What is the problem with this circuit?  Fix the problem identified and draw your circuit and expected output.

So after finishing this test, I had nothing to do since the interviews for VHDL were taking a very long time.  I found another guy who had finished his interview so we decided to take a stroll through Hamilton but we didn't get far from the office when it started to rain.  We waited underneath some shelter for a while, hoping that the rain would ease back.  But it didn't so we decided to go back into the office.  That was a bit sad.  We got back into the office and now more people had finished their interviews.  So the usual discussion about what questions were asked and feedback the interviewers gave began.  It didn't seem like anybody had much of an advantage.  Everybody got perplexed by the questions the interviewers asked.  The first guy who got interviewed for VHDL only got out after an hour and half of interviewing; which is a very long time, indeed.  Apparently they were asked to complete more questions on a whiteboard.

I never got the chance to get an interview with the VHDL guys which was a shame because it seemed more of appropriate to have been interviewed by them and I was up for the whiteboard challenge!  Well I was told that even though I didn't get interviewed, the VHDL test that I did should be enough for them to figure out if they wanted to interview me later on.  Hope they do, or hope that I got the Card job.  Either way, having a job in Auckland would be good.  That was pretty much the end of the day.  The cab had arrived so we were off back home!