Show HN: A realtime node-based audio synth based on LLVM • Hacker News Board

Re: Show HN: A realtime node-based audio synth based on LLVM

#21

Post by cpdt » Fri, Nov 02, 2018, 4:32 AM UTC

ssfrr wrote: post #20

cpdt wrote: post #11

Earlier quoted context omitted.

I haven't actually properly played around with PureData (other than watching a few videos on it back when I started this project), so I can't really comment too much on how that compares. I was initially worried about how interactive compiling would be, however it turns out (at least with the projects we've tested it with so far), it's pretty easily able to keep up with around 3ms from a modification to codegen being…

Thanks for replying, I'd definitely be interested in more architectural details. 3ms to complete codegen is orders of magnitude faster than I expected. Does that include everything necessary from making the change through actually synthesizing samples?

I'll look at writing that blog post soon then :)

Just did some proper testing on a reasonably complex project, looks like I was about an order of magnitude off (to be fair it was 2AM here at the time, and I wasn't reading the numbers right haha). 30-40ms is still fast enough that you don't notice for the most part though. For this specific project, it breaks down roughly like this:

- ~1ms to build the new MIR based on the editor state

- ~5ms to process/run passes on the MIR (this involves some funky graph traversal which could very likely be optimized a lot)

- ~12ms to generate LLVM IR

- ~14ms in the LLVM JIT

In a project that makes good use of groups (nodes that contain a surface inside and then expose some controls back out) I'd expect this to be lower, since we only need to perform those operations on the surfaces that change.

Re: Show HN: A realtime node-based audio synth based on LLVM

#22

Post by gmueckl » Fri, Nov 02, 2018, 4:58 AM UTC

cpdt wrote: post #21

ssfrr wrote: post #20

Earlier quoted context omitted.

Thanks for replying, I'd definitely be interested in more architectural details. 3ms to complete codegen is orders of magnitude faster than I expected. Does that include everything necessary from making the change through actually synthesizing samples?

I'll look at writing that blog post soon then :) Just did some proper testing on a reasonably complex project, looks like I was about an order of magnitude off (to be fair it was 2AM here at the time, and I wasn't reading the numbers right haha). 30-40ms is still fast enough that you don't notice for the most part though. For this specific project, it breaks down roughly like this: - ~1ms to build the new MIR based o…

Hm, 12ms for the IR is longer than I would expect for such a translation step. Do you know whwre this time is being spent?

Re: Show HN: A realtime node-based audio synth based on LLVM

#23

Post by cpdt » Fri, Nov 02, 2018, 5:41 AM UTC

gmueckl wrote: post #22

cpdt wrote: post #21

Earlier quoted context omitted.

I'll look at writing that blog post soon then :) Just did some proper testing on a reasonably complex project, looks like I was about an order of magnitude off (to be fair it was 2AM here at the time, and I wasn't reading the numbers right haha). 30-40ms is still fast enough that you don't notice for the most part though. For this specific project, it breaks down roughly like this: - ~1ms to build the new MIR based o…

Hm, 12ms for the IR is longer than I would expect for such a translation step. Do you know whwre this time is being spent?

Just had a look, and it turns out that's including running LLVM's optimizer as well, which takes roughly half the time. It's basically doing the equivalent of -O2 currently. That's probably more aggressive than what's needed, but I haven't taken the time to fine-tune it yet.

Other than that, you're right that it might be a bit high. There's very likely parts of the lowering code which can be optimized, I just haven't had the need to yet.