That function is only implemented for Float32/Float64: CUDA.jl/special_math.jl at 49902d8812a7796da313c39e4e9fe6d84a7309e9 · JuliaGPU/CUDA.jl · GitHub. I’m not familiar with the Bessel function; if it’s possible to express the operation on ComplexF32/F64 in terms of these that would make for a great addition to CUDA.jl.