# Automatically Accelerating ODEProblem Code

For some DEProblem types, automatic tracing functionality is already included via the modelingtoolkitize function. Take, for example, the Robertson ODE defined as an ODEProblem for DifferentialEquations.jl:

using DifferentialEquations
function rober(du,u,p,t)
y₁,y₂,y₃ = u
k₁,k₂,k₃ = p
du[1] = -k₁*y₁+k₃*y₂*y₃
du[2] =  k₁*y₁-k₂*y₂^2-k₃*y₂*y₃
du[3] =  k₂*y₂^2
nothing
end
prob = ODEProblem(rober,[1.0,0.0,0.0],(0.0,1e5),(0.04,3e7,1e4))

If we want to get a symbolic representation, we can simply call modelingtoolkitize on the prob, which will return an ODESystem:

sys = modelingtoolkitize(prob)

Using this, we can symbolically build the Jacobian and then rebuild the ODEProblem:

jac = eval(ModelingToolkit.generate_jacobian(sys)[2])
f = ODEFunction(rober, jac=jac)
prob_jac = ODEProblem(f,[1.0,0.0,0.0],(0.0,1e5),(0.04,3e7,1e4))