5 ms·

> If dynamic array bounds checking cost 5% (narrator: it is far less than that) It doesn’t work like that. If an image processing algorithm takes 2 instructio

> If dynamic array bounds checking cost 5% (narrator: it is far less than that) It doesn’t work like that. If an image processing algorithm takes 2 instructions per pixel, adding a check to every access could 3-4x the cost. This is why if you dictate bounds checking then the language becomes uncompetitive for certain tasks. The vast majority of cases it doesn’t matter at all - much less than 5%. I think safe/unsafe or general/performance scopes are a good way to handle this.

miloignis 1y ago
It's not that simple either - normally, if you're doing some loops over a large array of pixels, say, to perform some operation to them, there will only be a couple of bounds checks before the loop starts, checking the starting and ending conditions of the loops, not re-doing the bounds check for every pixel. So very rarely should it be anything like 3-4x the cost, though some complex indexing could cause it to happen, I suppose. I agree scopes are a decent way to handle it!
- monkeyelite 1y ago
  You’re describing a situation where I - or a very smart compiler can choose when to bounds check or not to make that intelligent realization.
timbit42 1y ago
Your argument is exactly why we ended up with the abominations of C and C++ instead of the safety of Pascal, Modula-2, Ada, Oberon, etc. Programmers at the time didn't realize how little impact safety features like bounds checking have. The bounds only need to be checked once for a for loop, not on each iteration.
- monkeyelite 1y ago
  > The bounds only need to be checked once for a for loop, not on each iteration. This is a theoretical argument. It depends on the compiler being able to see that’s what you’re doing and prove that there is no other mutation. > abominations of C and C++ Sounds like you don’t understand the design choices that made this languages successful.
  - timbit42 1y ago
    I understand the design choices and they're crap. Choosing a programming language shouldn't be a popularity contest.
    - timewizard 1y ago
      There are inevitably those who don't know how to program but are responsible for hiring those that can. Language popularity is an obvious metric with good utility for that case. Even so you haven't provided any compelling evidence that C or C++ made it's decisions to be more appealing or more popular.
Aurornis 1y ago
> It doesn’t work like that. If an image processing algorithm takes 2 instructions per pixel, adding a check to every access could 3-4x the cost. Your understanding of how bounds checking works in modern languages and compilers is not up to date. You're not going to find a situation where bounds checking causes an algorithm to take 3-4X longer. A lot of people are surprised when the bounds checking in Rust is basically negligible, maybe 5% at most. In many cases if you use iterators you might not see a hit at all. Then again, if you have an image processing algorithm that is literally reading every single pixel one-by-one to perform a 2-instruction operation and calculating bounds check on every access in the year 2025, you're doing a lot of things very wrong. > This is why if you dictate bounds checking then the language becomes uncompetitive for certain tasks. Do you have any examples at all? Or is this just speculation?
- monkeyelite 1y ago
  > Your understanding of how bounds checking works in modern languages and compilers is not up to date. One I am familiar with is Swift - which does exactly this because it’s a library feature of Array. Which languages will always be able to determine through function calls, indirect addressing, etc whether it needs to bounds check or not? And how will I know if it succeeded or whether something silently failed? > if you have an image processing algorithm that is literally reading every single pixel one-by-one to perform a 2-instruction operation and calculating bounds check on every access in the year 2025, you're doing a lot of things very wrong I agree. And note this is an example of a scenario you can encounter in other forms. > Do you have any examples at all? Or is this just speculation? Yes. Java and python are not competitive for graphics and audio processing.
  - MonkeyClub 1y ago
    > Java and python Java and Python are not on the same body of water, let alone the same boat. You can see some comparisons here: https://benchmarksgame-team.pages.debian.net/benchmarksgame/fastest/python.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
    - 1y ago

miloignis 1y ago

It's not that simple either - normally, if you're doing some loops over a large array of pixels, say, to perform some operation to them, there will only be a couple of bounds checks before the loop starts, checking the starting and ending conditions of the loops, not re-doing the bounds check for every pixel. So very rarely should it be anything like 3-4x the cost, though some complex indexing could cause it to happen, I suppose. I agree scopes are a decent way to handle it!

monkeyelite 1y ago
You’re describing a situation where I - or a very smart compiler can choose when to bounds check or not to make that intelligent realization.

timbit42 1y ago

Your argument is exactly why we ended up with the abominations of C and C++ instead of the safety of Pascal, Modula-2, Ada, Oberon, etc. Programmers at the time didn't realize how little impact safety features like bounds checking have. The bounds only need to be checked once for a for loop, not on each iteration.

monkeyelite 1y ago
> The bounds only need to be checked once for a for loop, not on each iteration. This is a theoretical argument. It depends on the compiler being able to see that’s what you’re doing and prove that there is no other mutation. > abominations of C and C++ Sounds like you don’t understand the design choices that made this languages successful.
- timbit42 1y ago
  I understand the design choices and they're crap. Choosing a programming language shouldn't be a popularity contest.
  - timewizard 1y ago
    There are inevitably those who don't know how to program but are responsible for hiring those that can. Language popularity is an obvious metric with good utility for that case. Even so you haven't provided any compelling evidence that C or C++ made it's decisions to be more appealing or more popular.

Aurornis 1y ago

> It doesn’t work like that. If an image processing algorithm takes 2 instructions per pixel, adding a check to every access could 3-4x the cost. Your understanding of how bounds checking works in modern languages and compilers is not up to date. You're not going to find a situation where bounds checking causes an algorithm to take 3-4X longer. A lot of people are surprised when the bounds checking in Rust is basically negligible, maybe 5% at most. In many cases if you use iterators you might not see a hit at all. Then again, if you have an image processing algorithm that is literally reading every single pixel one-by-one to perform a 2-instruction operation and calculating bounds check on every access in the year 2025, you're doing a lot of things very wrong. > This is why if you dictate bounds checking then the language becomes uncompetitive for certain tasks. Do you have any examples at all? Or is this just speculation?

monkeyelite 1y ago
> Your understanding of how bounds checking works in modern languages and compilers is not up to date. One I am familiar with is Swift - which does exactly this because it’s a library feature of Array. Which languages will always be able to determine through function calls, indirect addressing, etc whether it needs to bounds check or not? And how will I know if it succeeded or whether something silently failed? > if you have an image processing algorithm that is literally reading every single pixel one-by-one to perform a 2-instruction operation and calculating bounds check on every access in the year 2025, you're doing a lot of things very wrong I agree. And note this is an example of a scenario you can encounter in other forms. > Do you have any examples at all? Or is this just speculation? Yes. Java and python are not competitive for graphics and audio processing.
- MonkeyClub 1y ago
  > Java and python Java and Python are not on the same body of water, let alone the same boat. You can see some comparisons here: https://benchmarksgame-team.pages.debian.net/benchmarksgame/fastest/python.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
  - 1y ago