Platform-Independent SIMD in Go(go.dev)
103 pointsby yurivish3 hours ago9 comments
  • beached_whale9 minutes ago
    C++ is getting std::simd in the latest version and I am all aboard writing the vectorization with the least amount of intrinsic builtins I am able to. Even if not optimal, it's far better than the scalar ops.
  • qprofyeh3 hours ago
    This feature opens many doors for optimizing low-level performance in Go projects, that are already running multicore. IIRC there aren’t a lot of languages with built-in std lib support for SIMD and variants. Love the way Go is trying new stuff lately.
    • pjmlp2 hours ago
      Besides the usual C and C++, we have Java, .NET, D, Zig, Julia, Swift, Rust.

      So yeah, also appreciate having Go in the group instead of manually having to write Assembly.

      However not many languages adopt ways to manually write SIMD, because most of us have no idea how to write good SIMD code in first place, I surely don't.

      • stingraycharles2 hours ago
        Even with languages that adopt ways to manually write SIMD, it’s mostly left to library maintainers rather than application developers.

        I work for a C++ timeseries database startup that leverages SIMD about as much as we possibly can, and except for some extremely rare places we just use libraries.

        • pjmlpan hour ago
          Yeah, that is what I have heard from some NVidia folks as well, like Bryce Adelstein, use the libraries as much as possible, and leave the kernels for experts.

          However even then, it depends on how the libraries API surface looks like.

      • Thaxll2 hours ago
        With AI I'm pretty sure SIMD will be easier to integrate when necessary.
        • stingraycharlesan hour ago
          But it’s not necessary at all, the whole point is that these utility libraries bring you more elegant code that work on all platforms without having to pollute your codebase with SIMD intrinsics.

          Unless this was tongue in cheek, because this is in fact a problem with AI that it degrades your codebase in these types of ways.

        • pjmlpan hour ago
          With AI, I expect it to eventually be good enough for us to finally have 5 GLs, so it won't really matter.

          "CGO 2022 Keynote: Compiler 2.0"

          https://www.youtube.com/watch?v=w_sX9aZoZxg

    • abirch2 hours ago
      Vectorizing computations has been Matlabs secret sauce.
  • u8an hour ago
    This is why I love Go. Nobody was asking for this, but they took the time to do it right and continue to Push go as a memory safe, high-level systems language.
    • __san hour ago
      go data races aren't memory safe
    • OutOfHerean hour ago
      Go is in no way automatically memory safe. It's up to the programmer to write memory safe code with it.
  • vira2813 minutes ago
    This will welcome more database/warehouses to be written in Go.

    Personally I will implement it in https://github.com/viggy28/streambed

  • vlovich12339 minutes ago
    > The interface conversion and type switch look like they should be inefficient, but the compiler-side implementation of simd specializes code and optimizes away the type switch.

    I don’t understand this - how is it able to if the same go binary might run on unknown types? I’m assuming what it means is that the switch is implemented efficiently due to CPU branch prediction? I know fearless SIMD is doing cool stuff with static dispatch so that the feature set is checked just once at program start - is that what it means it’s doing under the hood? Very unclear.

    • Scaevolus30 minutes ago
      It creates multiple versions of functions referencing SIMD and lifts the dispatch switching cost to their callers.

      > The AST rewrite creates multiple specialized copies of functions, variables, and types that mention simd types, where simd types are replaced with references to size-specialized types in simd/internal/bridge. Each of these bridge types is defined as an archsimd type, but with a restricted set of methods. The specialized functions, variables, and types acquire a suffix of the form @simdNNN, where NNN is either a vector length (128, 256, or 512) or 0, indicating emulation. Functions that mention simd internally, but not in their signature, are converted to wrappers that switch on the SIMD level detected at program start, and call the appropriate specialized version of that function. Specialized functions call other specialized functions directly without dispatch overhead (and perhaps with inlining). This rewrite strategy was chosen as a compromise between code duplication and SIMD performance; the overhead is hoisted as high as necessary to avoid dispatch within SIMD computations, but not higher. If SIMD dispatch appears “too low” in a computation, a gratuitous mention of a simd type will move it upwards, as in this example:

  • physicsguy2 hours ago
    Oh this is great, it was one of my biggest bugbears about Go since you almost always have to link C/C++ code to get the appropriate performance.

    The one negative I'd say is that often autovectorisation is 'good enough' and this doesn't really tackle that gap.

    • typical1822 hours ago
      FWIW, there is some pretty substantial autovectorization work that is already in-flight for the Go compiler.

      There's a CL stack here:

      https://go.dev/cl/791740

      It's hard to make predictions with an open source project, but my personal guess is some flavor of it will land (including it is already demonstrating good results without an enormous level of code complexity in the compiler and without overly slowing down compile speeds), but I guess we'll see.

      It's being driven by an external contributor who has landed some good changes in the past to the Go compiler. (I think the autovectorization work might be part of their PhD or other academic research, but not sure.)

    • tgv2 hours ago
      As a first step, it might be possible to write a linter rule that rewrites suitable numeric loops to SIMD. There are already rules to rewrite several loop types, so that should be doable.
    • pjmlp2 hours ago
      The poor Assembler and the unsafe package forgotten in the corner.

      While reaching out to CGO is the easier way, it doesn't mean it is the only tool available in Go.

  • fatty_patty89an hour ago
    The problem with Go isn't performance but with the C/C++ interop overhead, even with the "30% less overhead" from a few updates ago which isnt true for 99% of cases, it isnt enough
    • victorbjorklund31 minutes ago
      Why is that the case? I don’t know low level programming so why is Go limited in interop with C?
  • karolistan hour ago
    Already using this for foreground estimation of cutouts in my project, around 30% speedup over non-SIMD, but the algorithm is probably not very optimised yet.
  • chrisjj34 minutes ago
    > Go 1.26 and 1.27 include experimental APIs for Single Instruction Multiple Data (SIMD) operations.

    You'd think these people would know the meaning of API, no?