Callback of DiffEq detecting "whether a certain condition has been satisfied for a given duration"

iHany · June 23, 2021, 10:25am

Hi,

is it possible in DifferentialEquations.jl to detect whether a certain condition has been satisfied for a given time duration?

SteffenPL · June 23, 2021, 10:40am

I’m no expert. I also cannot find a ready-made solution. Maybe you could do it yourself similar to this:

github.com

SciML/DiffEqCallbacks.jl/blob/master/src/autoabstol.jl

mutable struct AutoAbstolAffect{T}
    curmax::T
end
# Now make `affect!` for this:
function (p::AutoAbstolAffect)(integrator)
    if typeof(p.curmax) <: AbstractArray
        @. p.curmax = max(p.curmax, abs(integrator.u))
    else
        p.curmax = max(p.curmax, maximum(abs.(integrator.u)))
    end

    if typeof(integrator.opts.abstol) <: AbstractArray
        integrator.opts.abstol .= p.curmax .* integrator.opts.reltol
    else
        integrator.opts.abstol = p.curmax .* integrator.opts.reltol
    end

    u_modified!(integrator, false)
end

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Where instead of p.curmax you somehow store how long the condition is active already.

iHany · June 23, 2021, 2:22pm

It seems that there is no direct solution provided from DiffEq.jl.
Thanks a lot