Changing size of ODE system: resize! works but deleteat! doesn't

Specific Domains Numerics
5

It works when you specify the algorithm:

using DifferentialEquations
using Plots

const α = -0.3
function f(du,u,p,t)
  for i in 1:length(u)
    du[i] = α*u[i]
  end
end

function condition(u,t,integrator) # Event when event_f(u,t) == 0
  minimum(u)-0.01
end

function affect!(integrator)
  u = integrator.u
  #resize!(integrator,length(u)-1) # This works
  deleteat!(integrator, length(u)) # This errors
  nothing
end

callback = ContinuousCallback(condition,affect!)
u0 = [5, 3, 1]
tspan = (0.0,20.0)
prob = ODEProblem(f,u0,tspan)
sol = solve(prob,Tsit5(),callback=callback)

plot(sol.t,map((x)->length(x),sol[:]),lw=3,
     ylabel="Number of Cells",xlabel="Time")

The issue seems to be that if you use an automatic stiffness detection algorithm then, since they have some shared cache variables, it’s deleting from those shared cache variables twice. Could you file a bug report so we can track and get this fixed? It shouldn’t effect your usage if you select an algorithm, but it would be nice to fix it sooner or later.

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