The last bit of advice from Chad Fowler's
52 ways to save your job was to
be a generalist, so this week's version is the obvious opposite: to be a specialist.
The intersection point between the two seemingly disparate pieces of advice is that you shouldn't use your lack of experience in multiple technologies to call yourself a specialist in another. Just because you
develop in Java to the exclusion of .NET (or anything else) doesn't make you a Java specialist. To call yourself that,
you need to be "the authority" on all things Java.
Chad mentions a measure he used to assess a job candidate's depth of knowledge in Java: a question of how to make the
JVM crash.
I'm definitely lacking in this regard. I've got a pretty good handle on Java, Ruby, and ColdFusion. I've done a small amount of work in .NET and have been adding to that recently. I can certainly write a program that will crash - but can I write one to crash the virtual
machine (or CLR)?
I can relunctantly write small programs in C/C++, but I'm unlikely to have the patience to trace through a large program for fun. I might even still be able to figure out some assembly language if you gave me enough time. Certainly in these lower level items it's not hard to find a way to crash. It's
probably harder to
avoid it, in fact.
In ColdFusion, I've crashed the CF Server by simply writing recursive templates (those that
cfinclude themselves). (However, I don't know if that still works.) In Java and .NET, I wouldn't know where to start. What about crashing a browser with JavaScript?
So Chad mentions that you should know the internals of JVM and CLR. I should know how JavaScript works in the browser and not just how to
getElementById(). With that in mind, these things are going on the to-learn list - the goal being to find a way to crash each of them.
Ideas?
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Leave a comment
just crash it all
loop from one to 10 trillion
Posted by matt
on Sep 25, 2007 at 10:03 AM UTC - 5 hrs
Hi Matt- Thanks for the comments.
Would that compile (or would the compiler say that is too large of a number)? I'm confident that it would in C/C++ (or, at least it would not let me compile if I was trying to create an array that large), but I'm not sure about the others.
Running out of memory seems like a good way to crash it, but for that I'd need to create objects - not just iterate some large number of times.
I'll give it a shot some time just to try it out.
Posted by
Sam
on Sep 25, 2007 at 11:06 AM UTC - 5 hrs
Fun question!
One idea is to try and cause a stack overflow. You can do this with a recursive function that actually terminates (in theory!), but then call it with a huge value.
One thing to do is to *not* write it tail-recursively, as many compilers are smart enough to turn that into stack-friendly iterative code.
Try something like a simple non-tail-recursive factorial:
(defun fact (n)
(cond ((<= n 0) 1)
(t (* n (fact (- n 1))))))
(Note that I have the halt condition as (<= n 0), as I truly want this function to be convergent everywhere, not just for the non-negative inputs where it is classically defined.)
And call it upon something like 100000000:
(fact 100000000)
I can imagine that doing this in Java might crash the JVM with a stack-overflow. But, then again, I have no clue as to how clever these VM's are. I'm intrigued to learn!
Posted by
Grant
on Sep 25, 2007 at 06:58 PM UTC - 5 hrs
Hey, Sam,
I wonder, did you ever see if this works? Now I'm curious as to how clever the JVM is... :)
Grant
Posted by
grant
on Oct 01, 2007 at 06:51 PM UTC - 5 hrs
Hey Grant. I haven't taken the time to do it yet - I've been swamped on game programming in .NET and have yet to write a line of Java since then.
But, I do have your last message in my "action required" folder =)
I hope to have some free time by the weekend - this week I've got homeworks/presentation + work, so its been a long few days preparing for it all! =)
Posted by
Sam
on Oct 02, 2007 at 05:47 AM UTC - 5 hrs
Damn... I didn't realized it's been a week already! Guess I'm more backed up than I thought =)
Posted by
Sam
on Oct 02, 2007 at 05:50 AM UTC - 5 hrs
Sounds fun! I don't know anything about game programming. What kind of stuff are you doing?
P.S. It'd be interesting to see what happens in .NET when you try that factorial stack-breaker, too... :)
Posted by Grant
on Oct 04, 2007 at 11:35 AM UTC - 5 hrs
I'm basically making a 3D 3rd-person game in the vein of Super Mario Bros. with a twist. I'm using the XNA framework which will deploy to XBox 360, so that's kind of cool. I'm planning on writing a bit about it when I find the time.
I'll see if I can find a way to break .NET while I'm at it. =)
Posted by
Sam
on Oct 04, 2007 at 01:34 PM UTC - 5 hrs
Thanks Steev. I have yet to revisit this, so when I do, I'll give Ackermann a call.
Posted by
Sam
on Nov 02, 2007 at 05:41 AM UTC - 5 hrs
