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Comment by yulaow

13 hours ago

I am not in META but for what I read on blind, assuming it is true, they are not spending any time in long planning sessions or in getting into details of the implementation plan at all, and they could not anymore considering how many PRs in parallel they are requested to manage

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yulaow

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spacedcowboy  12 hours ago

Yeah, I'm retired. The only person I have to answer to regarding progress is me. I'm a stubborn son of a bitch when it comes to choosing quality over speed...

That doesn't mean I don't like progress mind :) This morning I got the preliminary results of a 'C' front-end to the compiler (it uses clang to compile to LLVM IR, then translates to our IR, then feeds that IR into the autovectoriser as if it had parsed the code itself). So for the exact same source code I now have:

     ┌─────────────┬────────────┬──────────────────────┬──────────┐
     │  Benchmark  │ clang -O2  │ xcc --par-auto (GPU) │ Speed-up │
     ├─────────────┼────────────┼──────────────────────┼──────────┤
     │ saxpy       │ 1,546 µs   │ 726 µs               │ 2.1×     │
     ├─────────────┼────────────┼──────────────────────┼──────────┤
     │ Mandelbrot  │ 394,238 µs │ 2,110 µs             │ 187×     │
     ├─────────────┼────────────┼──────────────────────┼──────────┤
     │ nbody       │ 37,090 µs  │ 1,035 µs             │ 36×      │
     ├─────────────┼────────────┼──────────────────────┼──────────┤
     │ perlin      │ 78,016 µs  │ 1,850 µs             │ 42×      │
     ├─────────────┼────────────┼──────────────────────┼──────────┤
     │ mandel_deep │ 73.2 s     │ 55.8 ms              │ 1,312×   │
     └─────────────┴────────────┴──────────────────────┴──────────┘

Those are some pretty fine speedups, from naive C, with no alterations from the standard "C" code - it automatically finds places that can be made data-parallel, tracks the data-hazards to make sure its safe to "GPU" and writes all the kernels, boilerplate and data-stream-management if necessary. Obviously the checksums have to match, so I know it did the work correctly too :)

Hacker News isn't interested - any post I make linking to the webpages is immediately blocked/dead so I'll wait until the C++ front-end is ready (some time next week) and announce it somewhere else. A compiler that takes standard C/C++ code and speeds it up by automatically finding data-parallel areas and scheduling them on the GPU with no programming overhead is pretty rare.

Oh, and it manages the local network as well, so you can run xcd on machines on your lan, or via the TB4/5 bridge between Macs and it'll schedule on other GPUs, just like it manages multiple GPUs on the local machine. It characterises both latency and compute-time to figure out which devices are worth scheduling on.

  • rpdillon  5 hours ago

    Awesome, this is genuinely-cool HN material. Thanks for sharing.

    • Silhouette  5 hours ago

      Upvotes don't appear publicly on HN so I'll comment to agree with this. I'm sorry if earlier information about this compiler got lost in the whirlwind. Data parallelism is a hard problem and these results look genuinely impressive so I for one would definitely be interested in hearing more about it and maybe discussing it further when there are interesting developments.

      1 reply →

  • jazzyjackson  5 hours ago

    Hell yea I love that computers are getting another chance at becoming compute fabric, just using each others GPUs. Sick.

  • bee_rider  5 hours ago

    So, the real input to your autovectorizer is LLVM IR; you could soon enough support any language that has an LLVM front-end? (I say soon enough instead of immediately because I’m sure there’s some manual wiring up to do). That seems like a pretty big deal. Do Fortran next, pls. :)

  • smokel  5 hours ago

    > Hacker News isn't interested

    I wouldn't be too sure about that :)

    • spacedcowboy  4 hours ago

      I’m being a little cynical - I’ve submitted it twice (though the ‘C’ front end is new) and it bombed both times - the second time within seconds of submission.

      I think it’s my own fault, I’ve posted the link to the compiler pages several times in what I thought were relevant posts, and I think HN thinks I’m spamming. So I’m not posting the home page for a while and we’ll see if a future submission “takes”

      2 replies →

  • ch_sm  6 hours ago

    That is pretty adventurous, but it sounds really cool! Will it be open source?

    • spacedcowboy  4 hours ago

      Yep. I’d give the link but I think HN thinks I’m spamming because I’ve mentioned it too many times before in posts - hence immediate death of any submission, so I’m not mentioning it for a while to see if that tails off.

      Bottom line: GPL3 for the compiler, standard library exclusions for derived works, so use it for anything but feed me back improvements to the compiler itself, and you don’t get to redistribute it as your own.