DifferentialEquations can solve backward?

General Usage
2

Did you mess up the order of arguments of the ODE right-hand side? It must be u, p, t for out-of-place problems (or du, u, p, t for in-place problems), see Ordinary Differential Equations · DifferentialEquations.jl. Here, u is the ODE solution (dependent variable), p are possible parameters, and t is the time (independent variable).

julia> using OrdinaryDiffEq # ODE part of DifferentialEquations

julia> f(u, params, time) = u
f (generic function with 1 method)

julia> ode_forward = ODEProblem(f, 1.0, (0.0, 1.0));

julia> sol_forward = solve(ode_forward, Tsit5());

julia> sol_forward.u[end], exp(1)
(2.718281708773342, 2.718281828459045)

julia> ode_backward = ODEProblem(f, 1.0, (0.0, -1.0));

julia> sol_backward = solve(ode_backward, Tsit5());

julia> sol_backward.u[end], exp(-1)
(0.3678795934275483, 0.36787944117144233)
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