pass init to prod in normalization (#81)

* pass init to prod in normalization

* Bounds check for region

Co-authored-by: Alex Arslan <ararslan@comcast.net>

* remove test for empty region

* add type assertion

* Add fallback checkindex method

* fixes to boundscheck

* Use init=1 in normalization

* Remove explicit bounds checking

* Use prod instead of mapreduce

* revert to using mapreduce

---------

Co-authored-by: Alex Arslan <ararslan@comcast.net>

Author: jishnub

src/definitions.jl

@@ -274,8 +274,9 @@ summary(p::ScaledPlan) = string(p.scale, " * ", summary(p.p))
 *(I::UniformScaling, p::Plan) = ScaledPlan(p, I.λ)
 *(p::Plan, I::UniformScaling) = ScaledPlan(p, I.λ)
 
-# Normalization for ifft, given unscaled bfft, is 1/prod(dimensions)
-normalization(::Type{T}, sz, region) where T = one(T) / Int(prod(sz[r] for r in region))::Int
+@inline function normalization(::Type{T}, sz, region) where T
+    one(T) / mapreduce(r -> Int(sz[r])::Int, *, region; init=1)::Int
+end
 normalization(X, region) = normalization(real(eltype(X)), size(X), region)
 
 plan_ifft(x::AbstractArray, region; kws...) =

test/runtests.jl

@@ -123,6 +123,9 @@ end
     # p::TestPlan)
     f9(p::AbstractFFTs.Plan{T}, sz) where {T} = AbstractFFTs.normalization(real(T), sz, fftdims(p))
     @test @inferred(f9(plan_fft(zeros(10), 1), 10)) == 1/10
+
+    @test_throws BoundsError AbstractFFTs.normalization(Float64, (2,), 1:3)
+    @test_throws BoundsError AbstractFFTs.normalization(Float64, (2,), (1,3,))
 end
 
 # Test that dims defaults to 1:ndims for fft-like functions