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Debunking the Google Interview Myth

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Re: Debunking the Google Interview Myth

#51

Post by strlen »

InclinedPlane wrote: post #44
strlen wrote: post #29

Earlier quoted context omitted.

Using a "magic marker" like this doesn't imply looking at a raw memory dump (which, however, is still needed in several places Google is involved e.g., kernel hacking, embedded devices). For example, I used it myself when debugging an issue where our processes morphed into un-killable zombies. I was dealing with crash dumps, where I was walking through the process list in the kernel (it's a doubly linked list) in cra…

If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining. If you want to find engineers with talent then you need to do a lot more leg-work in plumbing their knowledge, experience, and skill than merely ticking off a checklist of shibboleths. P.S. Personally I love hacker jargon and lore…

> If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining.

It's not about hacker folklore, it's about a debugging technique.

No one implies that this question is asked of every candidate. That's why these lists are useless. It's also not the way I'd ask a question about memory markers (I'd ask them about how they go about debugging such a problem and how the tools they use e.g., gdb and valgrind work), but it's a fair question to ask those claiming experience with or interest in low-level development much like it's fair to ask candidates who claim experience with data mining what the kernel trick is (...but it would be misleading to ask a Linux kernel hacker that question as that would mean something else to him, much as dead beef would mean something else to a data mining guru).

Re: Debunking the Google Interview Myth

#52

Post by sayrer »

ajg1977 wrote: post #18

I wonder about the technical knowledge of this person who's writing articles about hiring technical people. "Explain the significance of ‘dead beef'" is a perfectly valid, if somewhat unimaginative, technical question.

yeah, I've read this blog post before, and this bit has always stunk to me.

The pattern might be 0xDADADADA, 0xCAFEBABE, or 0xDEADBEEF. But it seems perfectly reasonable to ask what one might use this for. In fact, you'll find 0xDEADBEEF in the man page for libgmalloc.

(and all of the replies are about "raw memory" debugging... wtf)

Re: Debunking the Google Interview Myth

#54

Post by InclinedPlane »

strlen wrote: post #51
InclinedPlane wrote: post #44

Earlier quoted context omitted.

If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining. If you want to find engineers with talent then you need to do a lot more leg-work in plumbing their knowledge, experience, and skill than merely ticking off a checklist of shibboleths. P.S. Personally I love hacker jargon and lore…

> If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining. It's not about hacker folklore, it's about a debugging technique. No one implies that this question is asked of every candidate. That's why these lists are useless. It's also not the way I'd ask a question about memory markers (…

Keep in mind, I'm responding specifically to the idea that "[explaining] the significance of ‘dead beef'" is a valid interview question. Have you done a survey of memory debugging experts to determine how common knowledge of "dead beef" is?

It's not a knowledge question, it's a trivia question. A shibboleth. It is neither a necessary nor sufficient pre-condition for knowledge of memory debugging techniques and it probably has about as much correlation with them as asking whether they have read The Lord of the Rings.

Re: Debunking the Google Interview Myth

#55

Post by jwatzman »

[deleted] wrote: post #50
ajg1977 wrote: post #33

Earlier quoted context omitted.

The "right way" depends on the task at hand and the tools you have at your disposal. For any type of low-level work, being able to view, understand, and observe regions of memory is pretty much essential.

[deleted]

When I was writing a malloc implementation for a class, I defined a value I used in place of NULL to terminate a structure sort of like a linked list. With debugging off, it actually was defined to NULL; with debugging on, it was defined to 0xDEADBEEF so that I could see the distinctive value when debugging.

Re: Debunking the Google Interview Myth

#56

Post by strlen »

InclinedPlane wrote: post #54
strlen wrote: post #51

Earlier quoted context omitted.

> If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining. It's not about hacker folklore, it's about a debugging technique. No one implies that this question is asked of every candidate. That's why these lists are useless. It's also not the way I'd ask a question about memory markers (…

Keep in mind, I'm responding specifically to the idea that "[explaining] the significance of ‘dead beef'" is a valid interview question. Have you done a survey of memory debugging experts to determine how common knowledge of "dead beef" is? It's not a knowledge question, it's a trivia question. A shibboleth. It is neither a necessary nor sufficient pre-condition for knowledge of memory debugging techniques and it pro…

> It is neither a necessary nor sufficient pre-condition for knowledge of memory debugging techniques and it probably has about as much correlation with them as asking whether they have read The Lord of the Rings.

It's a hexadecimal number, that should be quite obvious. It's a noteable and easy to notice one. Others may have used a different one (I used 0x12341234 for the task as others have used 0xdeadbeef) but it should be obviously what you'd use it for.

Is it one of the better questions? No. Is it merely a shibboleth or a piece of trivia? When asked to low-level hackers, no.

Re: Debunking the Google Interview Myth

#57

Post by ssp »

bnoordhuis wrote: post #6

From anecdotal but first-hand experience (went through a couple of interview rounds), Google interviewers indeed don't ask the questions on that list. But the questions they do ask are hard and often academic - as in, you have likely never run into them in a real-world scenario before and you likely never will. At first I was like 'wow, Google must be populated with demi-gods'. Then I spoke to some Googlers off the r…

I think part of having the academic background is that it gives you the confidence to be casual about certain problems. When Google first demonstrated search suggestions, someone I know who is definitely a good programmer was very amazed that that it was possible to make something like that run fast enough, across the internet, no less.

But, if you have learned a little about indexing and data structures, you'll think "Yeah, you can probably generate k suggestions in something like O(k log n), and you can probably predict the next few characters that will be typed in, so that a lot of data could be cached on the client. This doesn't seem impossible", even if you can't come up with the exact algorithm right then and there.

That means you can design something like suggest or instant without getting stuck on whether it would run fast enough.

Or, conversely if the problem calls for solving an NP-hard problem, then you should get stuck on whether it can run fast enough and whether there is some way to approximate the answer instead. (Did anyone else check to see if you could get Google Maps to solve Traveling Salesman when they first added intermediate destinations?)

Re: Debunking the Google Interview Myth

#58

Post by zb »

wallflower wrote: post #40
moultano wrote: post #17

Earlier quoted context omitted.

probing you about stuff that even at Google's you won't be working on 5% of the time (if at all). In any highly skilled profession, 95% of the time someone with very little of your skill could do your job. The valuable part is that you can also be counted on for that 5% as well. Most of my time at Google hasn't involved any substantial theoretical work. One time though, I did have to come up with a algorithm for comp…

I'd like to believe this story (haven't found an authoritative source yet) that I heard once from a professional speaker of the FedEx main processing facility in Memphis. One day it completely stopped dead - usually it is controlled mayhem with the packages and machines running - the silence was deafening - thousands of dollars lost every minute. They brought in the best expert they could find. He investigated and we…

Apocryphal.

http://www.snopes.com/business/genius/where.asp

Re: Debunking the Google Interview Myth

#59

Post by Locke1689 »

InclinedPlane wrote: post #54
strlen wrote: post #51

Earlier quoted context omitted.

> If you want conformity that's fine. What would you think if your company instituted a very specific dress code? Requiring specific trivial knowledge is just as restrictive and constraining. It's not about hacker folklore, it's about a debugging technique. No one implies that this question is asked of every candidate. That's why these lists are useless. It's also not the way I'd ask a question about memory markers (…

Keep in mind, I'm responding specifically to the idea that "[explaining] the significance of ‘dead beef'" is a valid interview question. Have you done a survey of memory debugging experts to determine how common knowledge of "dead beef" is? It's not a knowledge question, it's a trivia question. A shibboleth. It is neither a necessary nor sufficient pre-condition for knowledge of memory debugging techniques and it pro…

No it's not. If you don't know about magic numbers you don't know how the BIOS loads the kernel into memory. Period.

Re: Debunking the Google Interview Myth

#60

Post by gcb »

code_duck wrote: post #45
adamdecaf wrote: post #7

Earlier quoted context omitted.

I know this attitude won't win very many friends, but I wouldn't accept a position where I wasn't asked to write code during the interview. I'm going to be writing code for money and they don't want me to prove that I can before hand? That's like hiring a "farmer" from the inner-city.

I'd take a look at a candidates github account or other open source work. That might preclude the need to ask for code during the interview.

most of my github account is filled with trash that i start for one day, barely learn something completely new to me, sometime a new language, then forget and move on.

if I find said thing promising, i'd usually came back some weekends later and do something more complex, but again, basically junk.

oh, and did i mention nothing looks finished?

Now, take anything i code behind the closed doors at my employer or i contribute to some open source projects. It will shine like nothing you will ever see in my github or googlecode or such.

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