DelayDiffEq.jl is a component package in the DifferentialEquations ecosystem. It holds the delay differential equation solvers and utilities. It is built on top of OrdinaryDiffEq to extend those solvers for delay differential equations. While completely independent and usable on its own, users interested in using this functionality should check out DifferentialEquations.jl.
DelayDiffEq.jl is part of the JuliaDiffEq common interface, but can be used independently of DifferentialEquations.jl. The only requirement is that the user passes a DelayDiffEq.jl algorithm to
solve. For example, we can solve the DDE tutorial from the documentation using the
using DelayDiffEq const p0 = 0.2; const q0 = 0.3; const v0 = 1; const d0 = 5 const p1 = 0.2; const q1 = 0.3; const v1 = 1; const d1 = 1 const d2 = 1; const beta0 = 1; const beta1 = 1; const tau = 1 function bc_model(du,u,h,p,t) du = (v0/(1+beta0*(h(p, t-tau)^2))) * (p0 - q0)*u - d0*u du = (v0/(1+beta0*(h(p, t-tau)^2))) * (1 - p0 + q0)*u + (v1/(1+beta1*(h(p, t-tau)^2))) * (p1 - q1)*u - d1*u du = (v1/(1+beta1*(h(p, t-tau)^2))) * (1 - p1 + q1)*u - d2*u end lags = [tau] h(p, t) = ones(3) tspan = (0.0,10.0) u0 = [1.0,1.0,1.0] prob = DDEProblem(bc_model,u0,h,tspan,constant_lags = lags) alg = MethodOfSteps(Tsit5()) sol = solve(prob,alg) using Plots; plot(sol)
Both constant and state-dependent lags are supported. Interfacing with OrdinaryDiffEq.jl for implicit methods for stiff equations is also supported.