Animation with threads in Plots.jl?

General Usage
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1

Since the canonical way of making animation involes:

anim = @animate for i in some_range
            plotting(blah...., i)
end
gif(anim, path_var)

is would be natural to parallelize this process since @animate IO a bunch of temp files to disks?

after looking at code base it appears that the current approach is to construct a big expression, having for loop and counter, at every frame use frame(plt = current()) calling png() to save to a file, which means this cannot be parallel because of the dependency on current() plot also file io.

2 Likes
2

Indeed, this would make a good PR :slight_smile:

3

ok at the moment the following minimal example would crash so it’s not trivial what to do

Threads.@threads for i = 2:10
    plot(1:1:i, rand(i))
    Plots.png(Plots.current(), "$i.png")
end

crash in Plots.png)

4

That is also using current() this

Threads.@threads for i = 2:10
    pl = plot(1:1:i, rand(i))
    Plots.png(pl, "$i.png")
end

would not, but now that I think of it, there is a lot of mutable global state in Plots, that this is also not threadsafe.

5

this would also fail, because png just would crash

6

The png part actually worked for me

plts = [ plot(rand(i)) for i in 2:10];
Threads.@threads for i = 1:9
       Plots.png(plts[i], "plt$i.png")
end
7

I believe that threads do not guarantee any specific execution order, so I’m not sure what type of animation you can make other than one with random frames.

8

no need to guarantee execution order if plots are fixed by index i

9

are you actually running more than 1 threads? Threads.nthreads()

what version of Julia and Plots is this, I get GR segmentation faults.