Merge pull request #439 from SomTambe/master

Add gradients for FilledExtrapolations

src/extrapolation/filled.jl

@@ -54,6 +54,16 @@ end
     return ret
 end
 
+@inline function Interpolations.gradient(etp::FilledExtrapolation{T}, x::Vararg{Number,N}) where {T,N}
+    itp = parent(etp)
+    if checkbounds(Bool, itp, x...)
+        gradient(itp, x...)
+    else
+        ptype = promote_type(eltype(itp), map(typeof, x)...)
+        return zeros(SVector{ndims(etp), ptype})
+    end
+end
+
 expand_index_resid_etp(deg, fillvalue, (l, u), x, etp::FilledExtrapolation, xN) =
     (l <= x <= u || Base.throw_boundserror(etp, xN))
 

test/gradient.jl

@@ -199,4 +199,37 @@ using Test, Interpolations, DualNumbers, LinearAlgebra
             end
         end
     end
+
+    @testset "Extrapolations" begin
+        # out of bounds extrapolation check where fillvalue=constant
+        dims = [1, 2, 3]
+        @testset "Constant Fillvalue" begin
+            dtypes = [Float32, Float64]
+            for dt in dtypes
+                for dm in dims
+                    itp = interpolate(rand(dt, ntuple(_ -> 5, dm)...), BSpline(Linear()))
+                    etp = extrapolate(itp, rand(dt)) # TODO: Add tests for different boundary conditions in extrapolate
+                    cs = ntuple(_->3, dm)
+                    @test @inferred(Interpolations.gradient(etp, cs...)) == @inferred(Interpolations.gradient(itp, cs...))
+                    for ds in [ntuple(_->-0.5, dm), ntuple(_->5.5, dm), ntuple(_->6, dm)]
+                        @test all(iszero, @inferred(Interpolations.gradient(etp, ds...)))
+                    end
+                end
+            end
+        end
+        @testset "Boundary Conditions" begin
+            BC = (Flat, Line, Periodic, Reflect, Natural)
+            for dm in dims
+                for bc in BC
+                    itp = interpolate(rand(5, 5), BSpline(Linear()))
+                    etp = extrapolate(itp, bc()) # TODO: Add tests for different boundary conditions in extrapolate
+                    cs = ntuple(_->3, 2)
+                    @test @inferred(Interpolations.gradient(etp, cs...)) == @inferred(Interpolations.gradient(itp, cs...))
+                    for ds in [ntuple(_->-0.5, 2), ntuple(_->5.5, 2), ntuple(_->6, 2)]
+                        @test size(@inferred(Interpolations.gradient(etp, ds...))) == (2,)
+                    end
+                end
+            end
+        end
+    end
 end