Possible garbage collection interaction with Juno

Hi,

I’m trying to figure out what’s happening here. Running the following example:

using DifferentialEquations, Plots


function usode!(du,u,p,t)
    C1 = 1.63e-9
    RS = 791.0
    C2 = 3.3e-9
    C0 = 0.3e-9
    L1 = 1e-3
    L2 = 82e-3
    CM = 4e-12
    LM = 8.0
    RM = 7500.0
    VC1, VC2, VC0, VCM, IL1, IL2, ILM, Vp = u
    fv, VAmag = p
    VA = VAmag*sinpi(2*Vp)
    du[1] = 1/C1*IL1
    du[2] = -1/C2*IL1
    du[3] = 1/C0*(IL1-IL2-ILM)
    du[4] = 1/CM*ILM
    du[5] = 1/L1*(VA-VC1-VC0-VC2-IL1*RS)
    du[6] = 1/L2*VC0
    du[7] = 1/LM*(VC0-VCM-ILM*RM)
    du[8] = fv
end

mutable struct Controller
    f::Float64
end
function(c::Controller)(integrator)
    integrator.p[1] = c.f
    if c.f < 30000.0
        c.f += 15.0
    end
    #println(integrator.t)
end

function sim()
    p = [0.0, 100.0]
    cb1 = PeriodicCallback(Controller(27000.0),0.005)
    cbs = CallbackSet(cb1,)
    u0 = [0.0,0.0,0.0,0.0, 0.0,0.0,0.0, 0.0]
    tspan = [0.0, 1.1]
    prob = ODEProblem(usode!,u0,tspan,p)
    @time sol = solve(prob,Tsit5(), callback=cbs, reltol=1e-8, abstol=1e-8, maxiters=10_000_000)
    sol
end

sol = sim()
sol=nothing
sol=sim()
sol=nothing
sol=sim()
sol=nothing
sol=sim()

The sim() call makes an object that nearly consumes my computer’s RAM. On the repeated executions, the memory gets released (garbage collected) and then we build it again.

After completion of the script, if I execute another sol=nothing followed by sol=sim() (either by doing Ctrl-Enter on the appropriate lines, or by typing the commands in at the REPL), the memory does not get released (and my computer crawls to a halt). I suspect something different happens in the Juno environment that prevents the previous sol object from getting collected. Adding a GC.gc() does not seem to help here.

Any thoughts as to what’s going on?

I can repro the issue (at least in Juno, I didn’t try outside of it).
It seems likely that we’re accidentally holding on to a reference for the result bubbles/workspace.

We’ll keep track of the issue at

1 Like

Thank you!