Add native GPU support.

Project.toml

@@ -3,6 +3,7 @@ uuid = "a98d9a8b-a2ab-59e6-89dd-64a1c18fca59"
 version = "0.14.0"
 
 [deps]
+Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
 AxisAlgorithms = "13072b0f-2c55-5437-9ae7-d433b7a33950"
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
@@ -31,11 +32,12 @@ DualNumbers = "fa6b7ba4-c1ee-5f82-b5fc-ecf0adba8f74"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SharedArrays = "1a1011a3-84de-559e-8e89-a11a2f7dc383"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["OffsetArrays", "Unitful", "SharedArrays", "ForwardDiff", "LinearAlgebra", "DualNumbers", "Random", "Test", "Zygote", "ColorVectorSpace"]
+test = ["OffsetArrays", "Unitful", "SharedArrays", "ForwardDiff", "LinearAlgebra", "DualNumbers", "Random", "Pkg", "Test", "Zygote", "ColorVectorSpace"]

docs/src/devdocs.md

@@ -55,6 +55,8 @@ concrete subtypes:
 General `AbstractArray`s may be indexed with `WeightedIndex` indices,
 and the result produces the interpolated value. In other words, the end result
 is just `itp.coefs[wis...]`, where `wis` is a tuple of `WeightedIndex` indices.
+To make sure this overloading is effective, we wrap the `coefs` with `InterpGetindex`，
+i.e. `InterpGetindex(itp.coefs)[wis...]`
 
 Derivatives along a particular axis can be computed just by substituting a component of `wis` for one that has been designed to compute derivatives rather than values.
 
@@ -107,7 +109,7 @@ Interpolations.WeightedAdjIndex{2, Float64}(1, (0.6000000000000001, 0.3999999999
 julia> wis[3]
 Interpolations.WeightedAdjIndex{2, Float64}(1, (0.30000000000000004, 0.7))
 
-julia> A[wis...]
+julia> Interpolations.InterpGetindex(A)[wis...]
 8.7
 ```
 
@@ -125,7 +127,7 @@ This computed the value of `itp` at `x...` because we called `weightedindexes` w
 
 !!! note
     Remember that prefiltering is not used for `Linear` interpolation.
-    In a case where prefiltering is used, we would substitute `itp.coefs[wis...]` for `A[wis...]` above.
+    In a case where prefiltering is used, we would substitute `InterpGetindex(itp.coefs)[wis...]` for `InterpGetindex(A)[wis...]` above.
 
 To compute derivatives, we *also* pass additional functions like [`Interpolations.gradient_weights`](@ref):
 
@@ -142,13 +144,13 @@ julia> wis[2]
 julia> wis[3]
 (Interpolations.WeightedAdjIndex{2,Float64}(1, (0.8, 0.19999999999999996)), Interpolations.WeightedAdjIndex{2,Float64}(1, (0.6000000000000001, 0.3999999999999999)), Interpolations.WeightedAdjIndex{2,Float64}(1, (-1.0, 1.0)))
 
-julia> A[wis[1]...]
+julia> Interpolations.InterpGetindex(A)[wis[1]...]
 1.0
 
-julia> A[wis[2]...]
+julia> Interpolations.InterpGetindex(A)[wis[2]...]
 3.000000000000001
 
-julia> A[wis[3]...]
+julia> Interpolations.InterpGetindex(A)[wis[3]...]
 9.0
 ```
 In this case you can see that `wis` is a 3-tuple-of-3-tuples. `A[wis[i]...]` can be used to compute the `i`th component of the gradient.
@@ -168,3 +170,29 @@ The code to do this replacement is a bit complicated due to the need to support
 It makes good use of *tuple* manipulations, sometimes called "lispy tuple programming."
 You can search Julia's discourse forum for more tips about how to program this way.
 It could alternatively be done using generated functions, but this would increase compile time considerably and can lead to world-age problems.
+
+### GPU Support
+At present, `Interpolations.jl` supports interpolant usage on GPU via broadcasting.
+
+A basic work flow looks like:
+```julia
+julia> using Interpolations, Adapt, CUDA # Or any other GPU package
+
+julia > itp = Interpolations.interpolate([1, 2, 3], (BSpline(Linear()))); # construct the interpolant object on CPU
+
+julia> cuitp = adapt(CuArray{Float32}, itp); # adapt it to GPU memory
+
+julia > cuitp.(1:0.5:2) # call interpolant object via broadcast
+
+julia> gradient.(Ref(cuitp), 1:0.5:2)
+```
+
+To achieve this, an `ITP <: AbstractInterpolation` should define it's own `Adapt.adapt_structure(to, itp::ITP)`, which constructs a new `ITP` with the adapted
+fields (`adapt(to, itp.fieldname)`) of `itp`. The field adaption could be skipped
+if we know that it has been GPU-compatable, e.g. a `isbit` range.
+
+!!! note
+    Some adaptors may change the storage type. Please ensure that the adapted `itp`
+    has the correct element type via the method `eltype`.
+
+Also, all GPU-compatable `AbstractInterpolation`s should define their own `Interpolations.root_storage_type`. This function allows us to modify the broadcast mechanism by overloading the default `BroadcastStyle`. See [Customizing broadcasting](https://docs.julialang.org/en/v1/manual/interfaces/#man-interfaces-broadcasting) for more details.

src/Interpolations.jl

@@ -41,7 +41,7 @@ using StaticArrays, WoodburyMatrices, Ratios, AxisAlgorithms, OffsetArrays
 using ChainRulesCore, Requires
 
 using Base: @propagate_inbounds, HasEltype, EltypeUnknown, HasLength, IsInfinite,
-    SizeUnknown
+    SizeUnknown, Indices
 import Base: convert, size, axes, promote_rule, ndims, eltype, checkbounds, axes1,
     iterate, length, IteratorEltype, IteratorSize, firstindex, getindex, LogicalIndex
 
@@ -269,76 +269,32 @@ Base.:(/)(wi::WeightedArbIndex, x::Number) = WeightedArbIndex(wi.indexes, wi.wei
 
 ### Indexing with WeightedIndex
 
-# We inject indexing with `WeightedIndex` at a non-exported point in the dispatch heirarchy.
-# This is to avoid ambiguities with methods that specialize on the array type rather than
-# the index type.
-Base.to_indices(A, I::Tuple{Vararg{Union{Int,WeightedIndex}}}) = I
-if VERSION < v"1.6.0-DEV.104"
-    @propagate_inbounds Base._getindex(::IndexLinear, A::AbstractVector, i::Int) = getindex(A, i)  # ambiguity resolution
+# We inject `WeightedIndex` as a non-exported indexing point with a `InterpGetindex` wrapper.
+# `InterpGetindex` is not a subtype of `AbstractArray`. This ensures that the overload applies to all array types.
+struct InterpGetindex{N,A<:AbstractArray{<:Any,N}}
+    coeffs::A
+    InterpGetindex(itp::AbstractInterpolation) = InterpGetindex(coefficients(itp))
+    InterpGetindex(A::AbstractArray) = new{ndims(A),typeof(A)}(A)
 end
-@inline function Base._getindex(::IndexStyle, A::AbstractArray{T,N}, I::Vararg{Union{Int,WeightedIndex},N}) where {T,N}
-    interp_getindex(A, I, ntuple(d->0, Val(N))...)
-end
-
-# The non-generated version is currently disabled due to https://github.com/JuliaLang/julia/issues/29117
-# # This follows a "move processed indexes to the back" strategy, so J contains the yet-to-be-processed
-# # indexes and I all the processed indexes.
-# interp_getindex(A::AbstractArray{T,N}, J::Tuple{Int,Vararg{Any,L}}, I::Vararg{Int,M}) where {T,N,L,M} =
-#     interp_getindex(A, Base.tail(J), I..., J[1])
-# function interp_getindex(A::AbstractArray{T,N}, J::Tuple{WeightedIndex,Vararg{Any,L}}, I::Vararg{Int,M}) where {T,N,L,M}
-#     wi = J[1]
-#     interp_getindex1(A, indexes(wi), weights(wi), Base.tail(J), I...)
-# end
-# interp_getindex(A::AbstractArray{T,N}, ::Tuple{}, I::Vararg{Int,N}) where {T,N} =   # termination
-#     @inbounds A[I...]  # all bounds-checks have already happened
-#
-# ## Handle expansion of a single dimension
-# # version for WeightedAdjIndex
-# @inline interp_getindex1(A, i::Int, weights::NTuple{K,Any}, rest, I::Vararg{Int,M}) where {M,K} =
-#     weights[1] * interp_getindex(A, rest, I..., i) + interp_getindex1(A, i+1, Base.tail(weights), rest, I...)
-# @inline interp_getindex1(A, i::Int, weights::Tuple{Any}, rest, I::Vararg{Int,M}) where M =
-#     weights[1] * interp_getindex(A, rest, I..., i)
-# interp_getindex1(A, i::Int, weights::Tuple{}, rest, I::Vararg{Int,M}) where M =
-#     error("exhausted the weights, this should never happen")
-#
-# # version for WeightedArbIndex
-# @inline interp_getindex1(A, indexes::NTuple{K,Int}, weights::NTuple{K,Any}, rest, I::Vararg{Int,M}) where {M,K} =
-#     weights[1] * interp_getindex(A, rest, I..., indexes[1]) + interp_getindex1(A, Base.tail(indexes), Base.tail(weights), rest, I...)
-# @inline interp_getindex1(A, indexes::Tuple{Int}, weights::Tuple{Any}, rest, I::Vararg{Int,M}) where M =
-#     weights[1] * interp_getindex(A, rest, I..., indexes[1])
-# interp_getindex1(A, indexes::Tuple{}, weights::Tuple{}, rest, I::Vararg{Int,M}) where M =
-#     error("exhausted the weights and indexes, this should never happen")
-
-@inline interp_getindex(A::AbstractArray{T,N}, J::Tuple{Int,Vararg{Any,K}}, I::Vararg{Int,N}) where {T,N,K} =
-    interp_getindex(A, Base.tail(J), Base.tail(I)..., J[1])
-@generated function interp_getindex(A::AbstractArray{T,N}, J::Tuple{WeightedAdjIndex{L,W},Vararg{Any,K}}, I::Vararg{Int,N}) where {T,N,K,L,W}
-    ex = :(w[1]*interp_getindex(A, Jtail, Itail..., j))
-    for l = 2:L
-        ex = :(w[$l]*interp_getindex(A, Jtail, Itail..., j+$(l-1)) + $ex)
-    end
-    quote
-        $(Expr(:meta, :inline))
-        Jtail = Base.tail(J)
-        Itail = Base.tail(I)
-        j, w = J[1].istart, J[1].weights
-        $ex
-    end
-end
-@generated function interp_getindex(A::AbstractArray{T,N}, J::Tuple{WeightedArbIndex{L,W},Vararg{Any,K}}, I::Vararg{Int,N}) where {T,N,K,L,W}
-    ex = :(w[1]*interp_getindex(A, Jtail, Itail..., ij[1]))
-    for l = 2:L
-        ex = :(w[$l]*interp_getindex(A, Jtail, Itail..., ij[$l]) + $ex)
-    end
-    quote
-        $(Expr(:meta, :inline))
-        Jtail = Base.tail(J)
-        Itail = Base.tail(I)
-        ij, w = J[1].indexes, J[1].weights
-        $ex
-    end
-end
-@inline interp_getindex(A::AbstractArray{T,N}, ::Tuple{}, I::Vararg{Int,N}) where {T,N} =   # termination
-    @inbounds A[I...]  # all bounds-checks have already happened
+@inline Base.getindex(A::InterpGetindex{N}, I::Vararg{Union{Int,WeightedIndex},N}) where {N} =
+    interp_getindex(A.coeffs, ntuple(_ -> 0, Val(N)), map(indexflag, I)...)
+indexflag(I::Int) = I
+@inline indexflag(I::WeightedIndex) = indextuple(I), weights(I)
+
+# A recursion-based `interp_getindex`, which follows a "move processed indexes to the back" strategy
+# `I` contains the processed index, and (wi1, wis...) contains the yet-to-be-processed indexes
+# Here we meet a no-interp dim, just append the index to `I`'s end.
+@inline interp_getindex(A, I, wi1::Int, wis...) =
+    interp_getindex(A, (Base.tail(I)..., wi1), wis...)
+# Here we handle the expansion of a single dimension.
+@inline interp_getindex(A, I, wi1::NTuple{2,Tuple{Any,Vararg{Any,N}}}, wis...) where {N} =
+    wi1[2][end] * interp_getindex(A, (Base.tail(I)..., wi1[1][end]), wis...) +
+    interp_getindex(A, I, map(Base.front, wi1), wis...)
+@inline interp_getindex(A, I, wi1::NTuple{2,Tuple{Any}}, wis...) =
+    wi1[2][1] * interp_getindex(A, (Base.tail(I)..., wi1[1][1]), wis...)
+# Termination
+@inline interp_getindex(A::AbstractArray{T,N}, I::Dims{N}) where {T,N} =
+    @inbounds A[I...] # all bounds-checks have already happened
 
 """
     w = value_weights(degree, δx)
@@ -489,6 +445,9 @@ include("lanczos/lanczos_opencv.jl")
 include("iterate.jl")
 include("chainrules/chainrules.jl")
 include("hermite/cubic.jl")
+if VERSION >= v"1.6"
+    include("gpu_support.jl")
+end
 
 function __init__()
     @require Unitful="1986cc42-f94f-5a68-af5c-568840ba703d" include("requires/unitful.jl")

src/b-splines/b-splines.jl

@@ -66,7 +66,7 @@ However, for customized control you may also construct them with
 where `T` gets computed from the product of `TWeights` and `eltype(coefs)`.
 (This is equivalent to indicating that you'll be evaluating at locations `itp(x::TWeights, y::TWeights, ...)`.)
 """
-struct BSplineInterpolation{T,N,TCoefs<:AbstractArray,IT<:DimSpec{BSpline},Axs<:Tuple{Vararg{AbstractUnitRange,N}}} <: AbstractInterpolation{T,N,IT}
+struct BSplineInterpolation{T,N,TCoefs<:AbstractArray,IT<:DimSpec{BSpline},Axs<:Indices{N}} <: AbstractInterpolation{T,N,IT}
     coefs::TCoefs
     parentaxes::Axs
     it::IT
@@ -78,6 +78,9 @@ function Base.:(==)(o1::BSplineInterpolation, o2::BSplineInterpolation)
     o1.coefs == o2.coefs
 end
 
+BSplineInterpolation{T,N}(A::AbstractArray, axs::Indices{N}, it::IT) where {T,N,IT} =
+    BSplineInterpolation{T,N,typeof(A),IT,typeof(axs)}(A, axs, it)
+
 function BSplineInterpolation(::Type{TWeights}, A::AbstractArray{Tel,N}, it::IT, axs) where {N,Tel,TWeights<:Real,IT<:DimSpec{BSpline}}
     # String interpolation causes allocation, noinline avoids that unless they get called
     @noinline err_concrete(IT) = error("The b-spline type must be a concrete type (was $IT)")
@@ -98,7 +101,7 @@ function BSplineInterpolation(::Type{TWeights}, A::AbstractArray{Tel,N}, it::IT,
     else
         T = typeof(zero(TWeights) * first(A))
     end
-    BSplineInterpolation{T,N,typeof(A),IT,typeof(axs)}(A, fix_axis.(axs), it)
+    BSplineInterpolation{T,N}(A, fix_axis.(axs), it)
 end
 
 function BSplineInterpolation(A::AbstractArray{Tel,N}, it::IT, axs) where {N,Tel,IT<:DimSpec{BSpline}}

src/b-splines/indexing.jl

@@ -5,7 +5,7 @@ itpinfo(itp) = (tcollect(itpflag, itp), axes(itp))
 @inline function (itp::BSplineInterpolation{T,N})(x::Vararg{Number,N}) where {T,N}
     @boundscheck (checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x))
     wis = weightedindexes((value_weights,), itpinfo(itp)..., x)
-    itp.coefs[wis...]
+    InterpGetindex(itp)[wis...]
 end
 @propagate_inbounds function (itp::BSplineInterpolation{T,N})(x::Vararg{Number,M}) where {T,M,N}
     inds, trailing = split_trailing(itp, x)
@@ -17,15 +17,15 @@ end
     @boundscheck (checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x))
     itps = tcollect(itpflag, itp)
     wis = dimension_wis(value_weights, itps, axes(itp), x)
-    coefs = coefficients(itp)
+    coefs = InterpGetindex(itp)
     ret = [coefs[i...] for i in Iterators.product(wis...)]
     reshape(ret, shape(wis...))
 end
 
 @propagate_inbounds function gradient(itp::BSplineInterpolation{T,N}, x::Vararg{Number,N}) where {T,N}
     @boundscheck checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x)
     wis = weightedindexes((value_weights, gradient_weights), itpinfo(itp)..., x)
-    return SVector(_gradient(itp.coefs, wis...))   # work around #311
+    return SVector(_gradient(InterpGetindex(itp), wis...))   # work around #311
 end
 @inline _gradient(coefs, inds, moreinds...) = (coefs[inds...], _gradient(coefs, moreinds...)...)
 _gradient(coefs) = ()
@@ -37,7 +37,7 @@ end
 @propagate_inbounds function hessian(itp::BSplineInterpolation{T,N}, x::Vararg{Number,N}) where {T,N}
     @boundscheck checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x)
     wis = weightedindexes((value_weights, gradient_weights, hessian_weights), itpinfo(itp)..., x)
-    symmatrix(map(inds->itp.coefs[inds...], wis))
+    symmatrix(map(inds->InterpGetindex(itp)[inds...], wis))
 end
 @propagate_inbounds function hessian!(dest, itp::BSplineInterpolation{T,N}, x::Vararg{Number,N}) where {T,N}
     dest .= hessian(itp, x...)

src/extrapolation/extrapolation.jl

@@ -71,8 +71,8 @@ end
         eflag = tcollect(etpflag, etp)
         xs = inbounds_position(eflag, bounds(itp), x, etp, x)
         g = @inbounds gradient(itp, xs...)
-        skipni = t->skip_flagged_nointerp(itp, t)
-        SVector(extrapolate_gradient.(skipni(eflag), skipni(x), skipni(xs), Tuple(g)))
+        skipni = Base.Fix1(skip_flagged_nointerp, itp)
+        SVector(map(extrapolate_gradient, skipni(eflag), skipni(x), skipni(xs), Tuple(g)))
     end
 end
 

src/gpu_support.jl

@@ -0,0 +1,72 @@
+import Adapt: adapt_structure
+using Adapt: adapt
+
+function adapt_structure(to, itp::BSplineInterpolation{T,N}) where {T,N}
+    coefs′ = adapt(to, itp.coefs)
+    T′ = update_eltype(T, coefs′, itp.coefs)
+    BSplineInterpolation{T′,N}(coefs′, itp.parentaxes, itp.it)
+end
+
+function update_eltype(T, coefs′, coefs)
+    ET = eltype(coefs′)
+    ET === eltype(coefs) && return T
+    WT = tweight(coefs′)
+    T′ = Base.promote_op(*, WT, ET)
+    (isconcretetype(T′) || isempty(coefs)) && return T′
+    return typeof(zero(WT) * convert(ET, first(coefs)))
+end
+
+function adapt_structure(to, itp::LanczosInterpolation{T,N}) where {T,N}
+    coefs′ = adapt(to, itp.coefs)
+    parentaxes′ = adapt(to, itp.parentaxes)
+    LanczosInterpolation{eltype(coefs′),N}(coefs′, parentaxes′, itp.it)
+end
+
+function adapt_structure(to, itp::GriddedInterpolation{T,N}) where {T,N}
+    coefs′ = adapt(to, itp.coefs)
+    knots′ = adapt(to, itp.knots)
+    T′ = update_eltype(T, coefs′, itp.coefs)
+    GriddedInterpolation{T′,N,typeof(coefs′),itptype(itp),typeof(knots′)}(knots′, coefs′, itp.it)
+end
+
+function adapt_structure(to, itp::ScaledInterpolation{T,N,<:Any,IT,RT}) where {T,N,IT,RT<:NTuple{N,AbstractRange}}
+    ranges = itp.ranges
+    itp′ = adapt(to, itp.itp)
+    ScaledInterpolation{eltype(itp′),N,typeof(itp′),IT,RT}(itp′, ranges)
+end
+
+function adapt_structure(to, itp::Extrapolation{T,N}) where {T,N}
+    et = itp.et
+    itp′ = adapt(to, itp.itp)
+    Extrapolation{eltype(itp′),N,typeof(itp′),itptype(itp),typeof(et)}(itp′, et)
+end
+
+import Base.Broadcast: broadcasted, BroadcastStyle
+using Base.Broadcast: broadcastable, combine_styles, AbstractArrayStyle
+function broadcasted(itp::AbstractInterpolation, args...)
+    args′ = map(broadcastable, args)
+    # we overload BroadcastStyle here (try our best to do broadcast on GPU)
+    style = combine_styles(Ref(itp), args′...)
+    broadcasted(style, itp, args′...)
+end
+
+"""
+    Interpolations.root_storage_type(::Type{<:AbstractInterpolation}) -> Type{<:AbstractArray}
+
+This function returns the type of the root cofficients array of an `AbstractInterpolation`.
+Some array wrappers, like `OffsetArray`, should be skipped.
+"""
+root_storage_type(::Type{T}) where {T<:Extrapolation} = root_storage_type(fieldtype(T, 1))
+root_storage_type(::Type{T}) where {T<:ScaledInterpolation} = root_storage_type(fieldtype(T, 1))
+root_storage_type(::Type{T}) where {T<:BSplineInterpolation} = root_storage_type(fieldtype(T, 1))
+root_storage_type(::Type{T}) where {T<:LanczosInterpolation} = root_storage_type(fieldtype(T, 1))
+root_storage_type(::Type{T}) where {T<:GriddedInterpolation} = root_storage_type(fieldtype(T, 2))
+root_storage_type(::Type{T}) where {T<:OffsetArray} = root_storage_type(fieldtype(T, 1))
+root_storage_type(::Type{T}) where {T<:AbstractArray} = T
+
+BroadcastStyle(::Type{<:Ref{T}}) where {T<:AbstractInterpolation} = _to_scalar_style(BroadcastStyle(T))
+BroadcastStyle(::Type{T}) where {T<:AbstractInterpolation} = BroadcastStyle(root_storage_type(T))
+
+_to_scalar_style(::S) where {S<:AbstractArrayStyle} = S(Val(0))
+_to_scalar_style(S::AbstractArrayStyle{Any}) = S
+_to_scalar_style(S) = S

src/gridded/indexing.jl

@@ -2,7 +2,7 @@
 @inline function (itp::GriddedInterpolation{T,N})(x::Vararg{Number,N}) where {T,N}
     @boundscheck (checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x))
     wis = weightedindexes((value_weights,), itpinfo(itp)..., x)
-    coefficients(itp)[wis...]
+    InterpGetindex(itp)[wis...]
 end
 @propagate_inbounds function (itp::GriddedInterpolation{T,N})(x::Vararg{Number,M}) where {T,M,N}
     inds, trailing = split_trailing(itp, x)
@@ -19,7 +19,7 @@ end
 @inline function gradient(itp::GriddedInterpolation{T,N}, x::Vararg{Number,N}) where {T,N}
     @boundscheck (checkbounds(Bool, itp, x...) || Base.throw_boundserror(itp, x))
     wis = weightedindexes((value_weights, gradient_weights), itpinfo(itp)..., x)
-    SVector(map(inds->coefficients(itp)[inds...], wis))
+    SVector(map(inds->InterpGetindex(itp)[inds...], wis))
 end
 
 itpinfo(itp::GriddedInterpolation) = (tcollect(itpflag, itp), itp.knots)
@@ -87,7 +87,7 @@ rescale_gridded(::typeof(hessian_weights), coefs, Δx) = coefs./Δx.^2
     else
         wis = dimension_wis(value_weights, itps, itp.knots, x)
     end
-    coefs = coefficients(itp)
+    coefs = InterpGetindex(itp)
     ret = [coefs[i...] for i in Iterators.product(wis...)]
     reshape(ret, shape(wis...))
 end