@cache struct KuttaPRK2p5Cache{uType, rateType, TabType} <: OrdinaryDiffEqMutableCache
    u::uType
    uprev::uType
    k::rateType
    k1::rateType
    k2::rateType
    k3::rateType
    k4::rateType
    k5_6::Array{rateType, 1}
    tmp::uType
    fsalfirst::rateType
    tab::TabType
end
get_fsalfirstlast(cache::KuttaPRK2p5Cache, u) = (cache.fsalfirst, cache.k)

struct KuttaPRK2p5ConstantCache{T, T2} <: OrdinaryDiffEqConstantCache
    α21::T
    α31::T
    α32::T
    α41::T
    α42::T
    α43::T
    α5_6::Array{T, 2}
    β1::T
    β3::T
    β5::T
    β6::T
    c2::T2
    c3::T2
    c4::T2
    c5_6::Array{T2, 1}

    function KuttaPRK2p5ConstantCache(T, T2)
        α21 = T(1 // 3)
        α31 = T(4 // 25)
        α32 = T(6 // 25)
        α41 = T(1 // 4)
        α42 = T(-3)
        α43 = T(15 // 4)

        α5_6 = Array{T}(undef, (2, 4))
        α5_6[1, 1] = T(6 // 81)
        α5_6[1, 2] = T(90 // 81)
        α5_6[1, 3] = T(-50 // 81)
        α5_6[1, 4] = T(8 // 81)
        α5_6[2, 1] = T(6 // 75)
        α5_6[2, 2] = T(36 // 75)
        α5_6[2, 3] = T(10 // 75)
        α5_6[2, 4] = T(8 // 75)

        β1 = T(23 // 192)
        β3 = T(125 // 192)
        β5 = T(-81 // 192)
        β6 = T(125 // 192)
        c2 = T2(1 // 3)
        c3 = T2(2 // 5)
        c4 = T2(1)
        c5_6 = Array{T2}(undef, 2)
        c5_6[1] = T2(2 // 3)
        c5_6[2] = T2(4 // 5)
        return new{T, T2}(
            α21, α31, α32, α41, α42, α43, α5_6, β1, β3, β5, β6, c2, c3, c4,
            c5_6
        )
    end
end

function alg_cache(
        alg::KuttaPRK2p5, u, rate_prototype, ::Type{uEltypeNoUnits},
        ::Type{uBottomEltypeNoUnits}, ::Type{tTypeNoUnits}, uprev, uprev2, f, t,
        dt, reltol, p, calck,
        ::Val{true}, verbose
    ) where {uEltypeNoUnits, uBottomEltypeNoUnits, tTypeNoUnits}
    tmp = zero(u)
    k = zero(rate_prototype)
    k1 = zero(rate_prototype)
    k2 = zero(rate_prototype)
    k3 = zero(rate_prototype)
    k4 = zero(rate_prototype)
    k5_6 = Array{typeof(rate_prototype)}(undef, 2)
    k5_6[1] = zero(rate_prototype)
    k5_6[2] = zero(rate_prototype)
    fsalfirst = zero(rate_prototype)
    tab = KuttaPRK2p5ConstantCache(
        constvalue(uBottomEltypeNoUnits),
        constvalue(tTypeNoUnits)
    )
    return KuttaPRK2p5Cache(u, uprev, k, k1, k2, k3, k4, k5_6, tmp, fsalfirst, tab)
end

function alg_cache(
        alg::KuttaPRK2p5, u, rate_prototype, ::Type{uEltypeNoUnits},
        ::Type{uBottomEltypeNoUnits}, ::Type{tTypeNoUnits}, uprev, uprev2, f, t,
        dt, reltol, p, calck,
        ::Val{false}, verbose
    ) where {uEltypeNoUnits, uBottomEltypeNoUnits, tTypeNoUnits}
    return KuttaPRK2p5ConstantCache(constvalue(uBottomEltypeNoUnits), constvalue(tTypeNoUnits))
end
