4 ms·

You shouldn’t rely on your tools protecting you because they won’t. I do part time work as an external examiner, sometimes for first year CS students, so I get

by jaabe 8y ago

You shouldn’t rely on your tools protecting you because they won’t. I do part time work as an external examiner, sometimes for first year CS students, so I get to see a lot of silly code. Like the result of having been tasked with doing Fibonacci recursively. Which, as most of you no doubt are aware, can be done correctly in several different ways. The most basic is to simply implement it with its two base cases and run it until you meet them for every sequence. A more efficient way is to implement it with a way of keeping track of Fibonacci sequences that you have already computed, as to not do them more than once. Both these ways work perfectly fine within the toolset, one just does it a lot better.

jschwartzi 8y ago
> This is a very basic example, but most students solve it the inefficient way, but in most situations you’d really rather have the ones who did it better. I would much rather have the student who solves it the inefficient way but who runs a profiler on their code with a real-world input, determines that their naive algorithm is unacceptably slow for certain inputs, and makes an adjustment to optimize it. If I'm only ever going to use the first 16 Fibonacci numbers I don't really care if they're brute-force computed recursively. I'd much rather spend valuable engineering time on optimizing something that actually matters. Requiring students to prematurely optimize some ivory tower algorithm as a precondition to working in the real world is precisely why we have a shortage in the first place. You should be training the students to optimize the algorithm when it needs to be optimized, and not just hiring people who've memorized a few very specific algorithms and can bark them on command during your interview.
- hinkley 8y ago
  My response would be “just use a loop and get it done so we can move onto the next task”. There are only two pieces of state here. Let’s not drag out the big guns and make something hard to read. Fibonacci is too simple a case to demonstrate the power of recursion, and people have beef with the textbook examples. It has a confounding factors that actually makes recursion an over complicated solution, and not enough factors to make it a good example for dynamic programming. Also it simply doesn’t scale to inputs that only take microseconds to calculate. It’s like those interview questions that leave you with more questions than answers, like “are they bad at interviews or just crazy?”
  - jschwartzi 8y ago
    Exactly. It's like a golden opportunity for me to demonstrate some engineering chops and instead the interviewer expects me to just whip out some caching implementation for some nebulous reason because that's what they would have done. If there's a real problem with either of our naive implementations the proper thing to do is to tell us what the problem is and leave us free to solve it.
hinkley 8y ago
? The most efficient way it to use iteration...
- scarface74 8y ago
  If I am paying them, the most efficient way is to use Google....
tonyedgecombe 8y ago
If I saw somebody solving it with iteration I would be suspicious that they have a problem with recursion. Unless performance was part of the problem of course.
Verdex 8y ago
| You shouldn’t rely on your tools protecting you because they won’t. Strong agree. It's like when your toilet overflows and instead of using a plunger (because sometimes this causes a splash that will get on your shoes) you just reach in with your bare hands. I've used this technique hundreds of times and I've never gotten any toilet water splashes on my shoes. [I get what you're trying to say, but it doesn't come off very well. All things being equal, tools are better than not tools. Being able to think and having tools is better yet, but why not give people tools if there are other options.]
- graphememes 8y ago
  How does a plunger protect you? Does the water harm your shoes or were you negligent to spray protectant on them? At some point, humans are involved and this requires a level of responsibility. Whether you're responsible for maintaining your tool, so that they don't break, or maintaining your shoes so that when something goes wrong there are safety measures in place to ensure minimal impact. I'd say these measures and responsibility marker a "good" "coder" and the lack of, marker a "bad" or "inexperienced" "coder". I'm using quotations because people enjoy to pontificate over language. Huge circle jerks that are a waste of time.
horsawlarway 8y ago
I don't really understand how this is relevant. Sure, memoization is more efficient for recursive fibonacci, but in both cases the code is correct. The author is presenting a case in which code is made demonstrably incorrect by seemingly unrelated changes, because those changes altered invariants about the objects the author was using - making his assumptions about which actions were safe incorrect. That's a good time for tooling to throw warnings/errors. Where you seem to be proposing... nothing?

by jaabe 8y ago

jschwartzi 8y ago

> This is a very basic example, but most students solve it the inefficient way, but in most situations you’d really rather have the ones who did it better. I would much rather have the student who solves it the inefficient way but who runs a profiler on their code with a real-world input, determines that their naive algorithm is unacceptably slow for certain inputs, and makes an adjustment to optimize it. If I'm only ever going to use the first 16 Fibonacci numbers I don't really care if they're brute-force computed recursively. I'd much rather spend valuable engineering time on optimizing something that actually matters. Requiring students to prematurely optimize some ivory tower algorithm as a precondition to working in the real world is precisely why we have a shortage in the first place. You should be training the students to optimize the algorithm when it needs to be optimized, and not just hiring people who've memorized a few very specific algorithms and can bark them on command during your interview.

hinkley 8y ago
My response would be “just use a loop and get it done so we can move onto the next task”. There are only two pieces of state here. Let’s not drag out the big guns and make something hard to read. Fibonacci is too simple a case to demonstrate the power of recursion, and people have beef with the textbook examples. It has a confounding factors that actually makes recursion an over complicated solution, and not enough factors to make it a good example for dynamic programming. Also it simply doesn’t scale to inputs that only take microseconds to calculate. It’s like those interview questions that leave you with more questions than answers, like “are they bad at interviews or just crazy?”
- jschwartzi 8y ago
  Exactly. It's like a golden opportunity for me to demonstrate some engineering chops and instead the interviewer expects me to just whip out some caching implementation for some nebulous reason because that's what they would have done. If there's a real problem with either of our naive implementations the proper thing to do is to tell us what the problem is and leave us free to solve it.

hinkley 8y ago

? The most efficient way it to use iteration...

scarface74 8y ago
If I am paying them, the most efficient way is to use Google....

tonyedgecombe 8y ago

If I saw somebody solving it with iteration I would be suspicious that they have a problem with recursion. Unless performance was part of the problem of course.

Verdex 8y ago

| You shouldn’t rely on your tools protecting you because they won’t. Strong agree. It's like when your toilet overflows and instead of using a plunger (because sometimes this causes a splash that will get on your shoes) you just reach in with your bare hands. I've used this technique hundreds of times and I've never gotten any toilet water splashes on my shoes. [I get what you're trying to say, but it doesn't come off very well. All things being equal, tools are better than not tools. Being able to think and having tools is better yet, but why not give people tools if there are other options.]

graphememes 8y ago
How does a plunger protect you? Does the water harm your shoes or were you negligent to spray protectant on them? At some point, humans are involved and this requires a level of responsibility. Whether you're responsible for maintaining your tool, so that they don't break, or maintaining your shoes so that when something goes wrong there are safety measures in place to ensure minimal impact. I'd say these measures and responsibility marker a "good" "coder" and the lack of, marker a "bad" or "inexperienced" "coder". I'm using quotations because people enjoy to pontificate over language. Huge circle jerks that are a waste of time.

horsawlarway 8y ago

I don't really understand how this is relevant. Sure, memoization is more efficient for recursive fibonacci, but in both cases the code is correct. The author is presenting a case in which code is made demonstrably incorrect by seemingly unrelated changes, because those changes altered invariants about the objects the author was using - making his assumptions about which actions were safe incorrect. That's a good time for tooling to throw warnings/errors. Where you seem to be proposing... nothing?