# Error Symbolic calculations could not initiate. Likely there's a function which is not differentiable by SymEngine

**URL:** <https://discourse.julialang.org/t/error-symbolic-calculations-could-not-initiate-likely-theres-a-function-which-is-not-differentiable-by-symengine/32707>\
**Category:** Numerics\
**Created:** [December 26, 2019, 6:16am UTC](https://discourse.julialang.org/t/error-symbolic-calculations-could-not-initiate-likely-theres-a-function-which-is-not-differentiable-by-symengine/32707 "2019-12-26T06:16:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yuxi.liu](https://avatars.discourse-cdn.com/v4/letter/y/839c29/32.png) [@yuxi.liu](https://discourse.julialang.org/u/yuxi.liu)\
**Post date:** [December 26, 2019, 6:16am UTC](https://discourse.julialang.org/t/error-symbolic-calculations-could-not-initiate-likely-theres-a-function-which-is-not-differentiable-by-symengine/32707/1 "2019-12-26T06:16:55Z")

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I’m simulating a satellite around the earth, and got error:  
`Symbolic calculations could not initiate. Likely there's a function which is not differentiable by SymEngine.`  
I think it’s because it cannot differentiate the -\frac 3 2 power. But how could it fail to differentiate something that simple?

```julia
using DifferentialEquations, ParameterizedFunctions

satellite! = @ode_def Satellite begin
    dx = vx
    dy = vy
    dvx = -GM*(x^2+y^2)^(-3//2) * x
    dvy = -GM*(x^2+y^2)^(-3//2) * y
end GM

G = 6.67e-11
M = 5.97e24
elasticity = 1
u0 = [0, 1e7, 5e3, 0]
tspan = (0.0,15.0)
p = [G*M] 

prob = ODEProblem(satellite!, u0, tspan, p)
sol = solve(prob,Tsit5())

```

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [December 26, 2019, 12:28pm UTC](https://discourse.julialang.org/t/error-symbolic-calculations-could-not-initiate-likely-theres-a-function-which-is-not-differentiable-by-symengine/32707/3 "2019-12-26T12:28:37Z")

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This is why we’ve moved away from SymEngine. However, that warning is completely harmless here since you’re using a non-stiff ODE solver.