Differential equations: Vern family solver, lazy option question

General Usage
1

For the Verner family solver of DifferentialEquations.jl, Vern6() through Vern9(), it is documented that the interpolation is “lazy” and

These methods when lazy assume that the parameter vector p will be unchanged between the moment of the interval solving and the interpolation. If p is changed in a ContinuousCallback, or in a DiscreteCallback and the continuous solution is used after the full solution, then set lazy=false .
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In my code, I used p to allocate the temporary matrix for things like mul! e.g.

hdim = 10

p = (
     x=zeros(Complex{Float64}, hdim, hdim), 
     y=zeros(Complex{Float64}, hdim, hdim)
)

and in the ode problem function, p.x, p.y, etc is used to hold temporary allocations, pseudo-code:

function f!(du,u,p,t)

...
mul!(p.x, a, b)
...

...
du .= p.x .+ p.y

end

so p changes during calculation (different p before and after f! gets called, and different p at different times). However, different input value of p does not change the calculation result since it’s always overwritten inside f!() with e.g. mul!(p.x, a, b). In this case, is the lazy=false option needed? Thanks a lot!

2

Nope, you’re fine.

1 Like
3

I thought so. Thanks a lot!