IIRC MacRuby used to compile to native code on OSX using LLVM, and was supposed to support native OSX APIs and Objective-C frameworks. It always seemed like a neat idea, and a slick integration, but I guess Apple moved to Swift instead.
I'll have to pick up a copy of this "Ruby Under a Microscope" book when the new version comes out. I've always liked Ruby, I just haven't had much chance to use it.
Typical. I may get absolutely destroyed for this, but being professionally proficient in a ton of languages, including Ruby and the ones I mention below, and the ones I'm about to mention:
This sounds like Microsoft when they moved from VB6 to VB.Net. At least they have a good thing going with C# though.
VB6 was quite an interesting beast. You could do basically everything that you could do in languages like C/C++, but in most cases, you could churn out code quicker. This even extended to DirectX/Direct3D! For Web pages? ASP Classic.
The tl;dr is that I really wish that ease of development were prioritized along with everything else. One of the reasons I like Ruby is the elegance of the language and ease of using it.
Note that I've been using it since the mid 2000s or so, but not exclusively (both it and VB6 defined my career, however). C# is my second most favorite.
If Ruby had the GUI design tools VB6 had, it would be interesting to look at the popularity stats
VB6 deserves the huge popularity it had, but the reason wasn't because of the language design, rather, its (extremely) rapid GUI application development. It was actually a two-edged sword - it facilitated writing spaghetti code.
> You could do basically everything that you could do in languages like C/C++
As long as there is some form of memory access, any language can do basically everything that one can do in C/C++, but this doesn't make much sense.
> As long as there is some form of memory access, any language can do basically everything that one can do in C/C++, but this doesn't make much sense.
No VB6 had really easy COM integration which let you tap into a lot of Windows system components. The same code in C++ often required hundreds of lines of scaffolding, and I'm not exaggerating
What about something like Shoes[1]? I have played with it a little, just to make a simple UI to run some scripts I can run fine in a shell myself, but less-technical people may be too scared to fire up Terminal.app in order to do the same...
Really happy to see Pat keeping it up! His first Ruby under a Microscope book but also his blog posts are amazing and a major source of inspiration for me. I did meet him personally in a Euruko conference. Such a great person.
Once a YJIT block executes enough times to warrant compilation, how does this system keep track of which types to compile for? Each block is tracking how many times it's entered, but not how many times it's entered for int or float or whatever types; so in the given example how would Ruby handle the compilation of the "opt_plus" stub when the input types may vary?
And by what process is the correct compiled block used depending on the input variable types?
That's the magic of YJIT, and what I'll describe in the rest of Chapter 4. YJIT uses a "wait-and-see" approach, and often defers compilation of the block/function until the actual types are provided by your program. And YJIT then keeps track of separate block versions based on the operand types, and can call the appropriate block version as needed.
This basic algorithm is called "Basic Block Versioning." Maxime Chevalier-Boisvert from Shopify has some great presentations online about this; for example [1].
I believe ZJIT, the newer JIT engine, uses a different approach. I'm exploring that now.
Glad to see that Ruby Under a Microscope is still being updated. It’s an essential read for anyone who wants to understand how Ruby works internally — and I truly enjoy reading it.
> To find hot spots, YJIT counts how many times your program calls each function or block
At first glance this seems too simple. Compare it to JavaScript JITs, which IIRC can compile hot spots even in functions that are only called a few times (e.g. those that contain heavy loops) via on-stack replacement. (Although I’ve also heard on-stack replacement called a “party trick” - more useful for optimising benchmark scores than for real code.)
But on the other hand, Ruby’s language design might help here. Idiomatic Ruby uses blocks for loop bodies - so can Ruby JITs optimise long-running loops by treating the loop body as just another function?
Yes that's something I want to dig into and explore in this chapter... when exactly does Ruby's JIT compiler activate and optimize our code? And you're right: since Ruby will JIT blocks as if they were separate function many loops will be optimized using this simple heuristic.
I find that using C as an intermediate step really helps conceptualize this process. It can be tough to imagine how to represent a language like ruby as C. Essentially you have to start from the point that everything is an object and method calls on objects, then build up from that. Then C to assembler is more manageable. Ymmv.
I always found the steps to assembler harder. I'd wish we could have both a hardware interface that is resembled at the same level as the software - but super simple. With that I mean super-simple to understand and write; assembler is simple but not easy to understand. The complexity scales quickly. That's why C was successful - it was much easier to reason about the system in C than it was in assembler/assembly.
I have a prototype ahead-of-time Ruby compiler. It's woefully incomplete - I've just recently picked it up again after years of inactivity, with heavy AI use to pursue rubyspec compliance (it's nowhere close). The point of mentioning that: MRI - the main Ruby interpreter - is fast enough that competing against it with an unoptimized compiler goes really badly unless you do a lot to optimise the garbage collector (I haven't yet).
So it's "fast". There's plenty more that can be done to make it much faster still, but even before yjit, MRI had gotten pretty decent.
I'll have to pick up a copy of this "Ruby Under a Microscope" book when the new version comes out. I've always liked Ruby, I just haven't had much chance to use it.
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