5 ms·

That's actually good your code breaks using new compilers as it means the code is bogus anyways. The alternatives to UB is either a strict spec that will be dog

That's actually good your code breaks using new compilers as it means the code is bogus anyways. The alternatives to UB is either a strict spec that will be dog slow on $arch or abstract away everything and make it complex.

saagarjha 8y ago
This isn't necessarily true. Many compiled languages these days have a strong specification that guarantees a lack of undefined behavior for the vast majority of code, yet remain relatively performant–think Swift, Rust, and the like.
pjmlp 8y ago
Being dog slow is very much dependent on the use case. Yes it will be slower than taking every shortcut in the name of performance. What really matters is, does the execution speed and memory footprint meat the requirements? If the user is happy to get their data in 100ms, with a requirement of 300ms max, getting it in 10ms is hardly an advantage.
- jjnoakes 8y ago
  If you can deliver responses 10x faster than required, you can scale with 10x fewer resources (or at least presumably some factor of fewer resources) and still stay within the user requirements. I'd say that's a nice advantage.
  - pjmlp 8y ago
    Not everyone is going to be the next Google, Facebook, Crytech, EA, ... There are better ways to waste money than spending it on YAGNI features.
    - jstimpfle 8y ago
      Consider Parkinson's law... Compare git to mercurial... Consider how many successful Java command line programs are there?
      - pjmlp 8y ago
        There are plenty of them at the enterprise level. Just a couple of months ago I re-wrote several Korn shell scripts doing ETL related tasks into a couple of saner Java CLI programs at customer request.
        jstimpfle 8y ago
        And the responsiveness is good? Isn't there always this terrible startup lag? Could we rewrite the C implementation of e.g. git in Java to get a program that is just as fast (e.g., instantaneous response for most operations)?
        pjmlp 8y ago
        Surely, you know that there are native code compilers for Java, right?
        jstimpfle 8y ago
        Is this practical? What are the limitations? Is this Java spirit? Why doesn't everybody use it? What does this do about startup time? My initial point in the meantime was only that performance does matter. And that for some reason I cannot recall any (open source or free software) CLI programs written in Java from the top of my head. While there are free Java implementations easily available no?
        pjmlp 8y ago
        Many don't use them, because they are commercial tools, and many developers nowadays don't like to pay for software. The only limitation is that for reflection code one needs to white list which classes end up on the binary. All major third party commercial JVMs always had the capability of AOT to native code, it was just tabu at Sun. Oracle has other point of view thus kept the Maxime project alive, rebranded it into Graal, and now those that don't like to pay for developer tools can also enjoy AOT compilation to native code via SubstrateVM, GraalVM and Graal integration into OpenJDK. Just Windows support is not yet fully done for the time being. Their long term roadmap is to rewrite the C++ parts of OpenJDK in Java itself, also known as Project Metropolis. OpenJDK 11 also adopted a feature already common in another commercial JVMs, which allows a JVM to dump a JIT image before existing. Which then allows for AOT like startup on the 2nd execution onwards. Also Java isn't the only safe alternative to C, those that don't mind lack of generics can just pick Go instead of dealing with C. Which then we already have several high profile projects using it, including Google's exploratory microkernel based OS.
  - slededit 8y ago
    These most recent optimizations are nowhere near 10x faster. The only one that can even come close is autovectorization and that can be done without heavy reliance on UB. If your loop is worth autovectorizing the 2 instructions to check for pointer aliasing, and other showstoppers is not material.
- MauranKilom 8y ago
  Correct, it depends on the use case. Nobody is saying you should write everything in C++. But there is plenty of software that actually uses your CPU for data processing where speed is absolutely crucial. If you know that every second (or 100 ms) saved in every functionality your software offers will eventually matter, would you still choose the more pessimistic performance guarantee? Did you know (at the point where the entire architecture was chosen) that you will get 100 ms with a safer language? What if you got 1000 ms and C++ got 100 ms?
  - pjmlp 8y ago
    Thing is, C and C++ aren't the only language with those capabilities, e.g. CPU for data processing. What to live on the danger zone and disable bounds checking on e.g. Turbo Pascal? Surround the critical performance code path with {$R-} and {$R+}, while enjoying safe bounds checking everywhere else.

saagarjha 8y ago

This isn't necessarily true. Many compiled languages these days have a strong specification that guarantees a lack of undefined behavior for the vast majority of code, yet remain relatively performant–think Swift, Rust, and the like.

pjmlp 8y ago

Being dog slow is very much dependent on the use case. Yes it will be slower than taking every shortcut in the name of performance. What really matters is, does the execution speed and memory footprint meat the requirements? If the user is happy to get their data in 100ms, with a requirement of 300ms max, getting it in 10ms is hardly an advantage.

jjnoakes 8y ago
If you can deliver responses 10x faster than required, you can scale with 10x fewer resources (or at least presumably some factor of fewer resources) and still stay within the user requirements. I'd say that's a nice advantage.
- pjmlp 8y ago
  Not everyone is going to be the next Google, Facebook, Crytech, EA, ... There are better ways to waste money than spending it on YAGNI features.
  - jstimpfle 8y ago
    Consider Parkinson's law... Compare git to mercurial... Consider how many successful Java command line programs are there?
    - pjmlp 8y ago
      There are plenty of them at the enterprise level. Just a couple of months ago I re-wrote several Korn shell scripts doing ETL related tasks into a couple of saner Java CLI programs at customer request.
      - jstimpfle 8y ago
        And the responsiveness is good? Isn't there always this terrible startup lag? Could we rewrite the C implementation of e.g. git in Java to get a program that is just as fast (e.g., instantaneous response for most operations)?
        pjmlp 8y ago
        Surely, you know that there are native code compilers for Java, right?
        jstimpfle 8y ago
        Is this practical? What are the limitations? Is this Java spirit? Why doesn't everybody use it? What does this do about startup time? My initial point in the meantime was only that performance does matter. And that for some reason I cannot recall any (open source or free software) CLI programs written in Java from the top of my head. While there are free Java implementations easily available no?
        pjmlp 8y ago
        Many don't use them, because they are commercial tools, and many developers nowadays don't like to pay for software. The only limitation is that for reflection code one needs to white list which classes end up on the binary. All major third party commercial JVMs always had the capability of AOT to native code, it was just tabu at Sun. Oracle has other point of view thus kept the Maxime project alive, rebranded it into Graal, and now those that don't like to pay for developer tools can also enjoy AOT compilation to native code via SubstrateVM, GraalVM and Graal integration into OpenJDK. Just Windows support is not yet fully done for the time being. Their long term roadmap is to rewrite the C++ parts of OpenJDK in Java itself, also known as Project Metropolis. OpenJDK 11 also adopted a feature already common in another commercial JVMs, which allows a JVM to dump a JIT image before existing. Which then allows for AOT like startup on the 2nd execution onwards. Also Java isn't the only safe alternative to C, those that don't mind lack of generics can just pick Go instead of dealing with C. Which then we already have several high profile projects using it, including Google's exploratory microkernel based OS.
- slededit 8y ago
  These most recent optimizations are nowhere near 10x faster. The only one that can even come close is autovectorization and that can be done without heavy reliance on UB. If your loop is worth autovectorizing the 2 instructions to check for pointer aliasing, and other showstoppers is not material.
MauranKilom 8y ago
Correct, it depends on the use case. Nobody is saying you should write everything in C++. But there is plenty of software that actually uses your CPU for data processing where speed is absolutely crucial. If you know that every second (or 100 ms) saved in every functionality your software offers will eventually matter, would you still choose the more pessimistic performance guarantee? Did you know (at the point where the entire architecture was chosen) that you will get 100 ms with a safer language? What if you got 1000 ms and C++ got 100 ms?
- pjmlp 8y ago
  Thing is, C and C++ aren't the only language with those capabilities, e.g. CPU for data processing. What to live on the danger zone and disable bounds checking on e.g. Turbo Pascal? Surround the critical performance code path with {$R-} and {$R+}, while enjoying safe bounds checking everywhere else.