Wrong derivative of exp(cos(x))
Opened this issue · 0 comments
astrozot commented
It seems to me that there is a problem with cos
derivatives in composite functions:
julia> D = (f, x) -> AbstractDifferentiation.derivative(DiffractorForwardBackend(), f, x)[1];
julia> D(x -> exp(cos(x)), 1.0)
-1.952024889228184
julia> exp(cos(1.0)) * (-sin(1.0))
-1.4444065708474794
julia> exp(sin(1.0)) * (-sin(1.0))
-1.952024889228184
Surprisingly, everything is OK with sin
derivatives:
julia> D(x -> exp(sin(x)), 1.0)
1.253380767493447
julia> exp(sin(1.0)) * cos(1.0)
1.253380767493447