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... Which is kind of worrying; is it really a good thing that processors are so complex that you need "decades" to use them to fully. Bottom line, you end up wi

... Which is kind of worrying; is it really a good thing that processors are so complex that you need "decades" to use them to fully. Bottom line, you end up with chaotic (in the "sensitive to the slightest change") performance behavior. OTOH this reminds of another saying, "don't roll your own crypto". But all those "don't" are a bit frustrating.

miloignis 4y ago
I've seen people get frustrated by the "don't"s before, but I think that's generally taking the first degree approximation too literally. Feel free to hand-write assembly or roll your own crypto, but don't depend on it for anything serious unless you are an expert or have it reviewed by one. Doing so for learning and fun is fine, if that's clearly called out such that no one accidentally depends on it for something serious. There's only one way to become good at something, and that's good practice! In a professional setting there's a responsibility to the end user which generally precludes doing these dangerous things - that is, one should feel free to take up woodworking as a hobby but shouldn't offer to build someone's house unless you're a licensed professional.
olliej 4y ago
But you don't need decades of experience: we have compilers and optimizers to do that.
- bioint7812 4y ago
  It's interesting that the impedence the author was experiencing was one of the CPU incorrectly "speculating" about the intent. We as readers are left to speculate about the problem being solved by the author. Based on the content of his recent articles, we could assume he is continuing his development of a JIT for a Rust port of his graphics engine. Given that assumption, I would argue that the compiler writers are lagging here--specifically lack of dynamic compilation. For example, is there a JIT compiler for the Rust language? I was thinking about reproducing his experiment in SBCL, which does have dynamic compilation--although it wouldn't be a real "apples" to "apples" comparison because my work machine is a x86_64.
  - olliej 4y ago
    JITs have very different constraints (but also many advantages) vs AOT compilers, so I don't think in the general case a language compiler can "support" JITs directly. llvm/clang for instance have a jit mode... for compiling C/C++, not some other language. Also obviously the compiler writers (AOT or JIT) need to know about and understand very minute details of how a cpu is behaving. I was responding to a person saying it was worrying that devs need that kind of knowledge and experience by saying that that isn't true because the tools exist (I feel that there's some analogy to what knowledge you need for a car: changing oil, servicing engine, replacing engine, designing an engine...). Once you are writing a JIT you're in the "making the tools" group, so you now need to know more than the vast majority of devs (not just more than the "average" dev) that's inescapable.
deleted 4y ago
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miloignis 4y ago

I've seen people get frustrated by the "don't"s before, but I think that's generally taking the first degree approximation too literally. Feel free to hand-write assembly or roll your own crypto, but don't depend on it for anything serious unless you are an expert or have it reviewed by one. Doing so for learning and fun is fine, if that's clearly called out such that no one accidentally depends on it for something serious. There's only one way to become good at something, and that's good practice! In a professional setting there's a responsibility to the end user which generally precludes doing these dangerous things - that is, one should feel free to take up woodworking as a hobby but shouldn't offer to build someone's house unless you're a licensed professional.

olliej 4y ago

But you don't need decades of experience: we have compilers and optimizers to do that.

bioint7812 4y ago
It's interesting that the impedence the author was experiencing was one of the CPU incorrectly "speculating" about the intent. We as readers are left to speculate about the problem being solved by the author. Based on the content of his recent articles, we could assume he is continuing his development of a JIT for a Rust port of his graphics engine. Given that assumption, I would argue that the compiler writers are lagging here--specifically lack of dynamic compilation. For example, is there a JIT compiler for the Rust language? I was thinking about reproducing his experiment in SBCL, which does have dynamic compilation--although it wouldn't be a real "apples" to "apples" comparison because my work machine is a x86_64.
- olliej 4y ago
  JITs have very different constraints (but also many advantages) vs AOT compilers, so I don't think in the general case a language compiler can "support" JITs directly. llvm/clang for instance have a jit mode... for compiling C/C++, not some other language. Also obviously the compiler writers (AOT or JIT) need to know about and understand very minute details of how a cpu is behaving. I was responding to a person saying it was worrying that devs need that kind of knowledge and experience by saying that that isn't true because the tools exist (I feel that there's some analogy to what knowledge you need for a car: changing oil, servicing engine, replacing engine, designing an engine...). Once you are writing a JIT you're in the "making the tools" group, so you now need to know more than the vast majority of devs (not just more than the "average" dev) that's inescapable.

deleted 4y ago

[deleted]