[PD] julia

[Spencer Russell]

Julia has a C-API so you can embed Julia the julia
interpreter/compiler/runtime into other applications by linking against
libjulia.so. It would be pretty doable to write a PD external that took
a julia module as an argument and called an agreed-to method (like
"process")

So you could define a julia module

module CoolNoise    function process{T <: Real}(out::Vector{Vector{T}},
in::Vector{Vector{T}}        for outvec in out            for i in
1:length(outvec)                outvec[i] = rand() * 2 - 1
end        end    end end

and maybe the object would be called [jl~] so you could instantiate [jl~
CoolNoise] and it would use your julia code to process blocks of audio.

I haven't thought much about whether this is the *best* way to do it,
but it would work. You'd need some other stuff in there to report back
the number and type of inlets/outlets, and probably some other stuff.

There are a few gotchas to writing latency-sensitive code in Julia,
particularly because it's garbage-collected so you want to be careful
not to write code that ends up doing a lot of heap allocation, but
there's been some work on the GC to speed it up, and in particular an
incremental GC that will yield control if the GC exceeds a time limit.
I've talked a bit to the guy working on it and while the current version
doesn't include his incremental code I think that with a little
encouragement (maybe a bottle of nice whiskey) he could be persuaded to
make it a reality. Aside from GC the other issue is that that JIT
compiler is a double-edged sword. Once things are compiled they're
really fast, but the process of compiling happens the first time a
method is called, so you need to make sure that any audio methods you
define get compiled before the main audio loop starts up. Julia is also
not thread-safe yet, though there are folks working on it, so calling
into julia code from multiple threads is a recipe for segfaults.

I wrote and maintain the AudioIO.jl[1] package which is an interactive
signal processing framework for Julia so I've spent some time thinking
about some of this. The project has lagged a bit while I've been
finishing up my (unrelated) masters thesis but this fall I'm going to be
digging much more deeply into it. I've actually considered implementing
the PD C API so I can pull PD externals into Julia,  basically the
inverse of this.

-s


On Mon, Aug 17, 2015, at 02:38 PM, Forrest Curo wrote:
> Any chances of adding Julia to the available languages for writing pd
> extensions? It seems to combine much of the writability of python with
> the specificity & machine-concreteness of C...
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Links:

  1. https://github.com/ssfrr/audioio.jl
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