Merge pull request #66 from Gregstrq/prealloc_fftshift

`fftshift!` and `ifftshift!`

Author: stevengj

src/AbstractFFTs.jl

@@ -5,7 +5,7 @@ import ChainRulesCore
 export fft, ifft, bfft, fft!, ifft!, bfft!,
        plan_fft, plan_ifft, plan_bfft, plan_fft!, plan_ifft!, plan_bfft!,
        rfft, irfft, brfft, plan_rfft, plan_irfft, plan_brfft,
-       fftshift, ifftshift, Frequencies, fftfreq, rfftfreq
+       fftshift, ifftshift, fftshift!, ifftshift!, Frequencies, fftfreq, rfftfreq
 
 include("definitions.jl")
 include("chainrules.jl")

src/definitions.jl

@@ -344,6 +344,16 @@ plan_irfft
 
 ##############################################################################
 
+"""
+    fftshift!(dest, src, [dim])
+
+Nonallocating version of [`fftshift`](@ref). Stores the result of the shift of the `src` array into the `dest` array.
+"""
+function fftshift!(dest, src, dim = 1:ndims(src))
+    s = ntuple(d -> d in dim ? div(size(dest,d),2) : 0, Val(ndims(dest)))
+    circshift!(dest, src, s)
+end
+
 """
     fftshift(x, [dim])
 
@@ -356,12 +366,21 @@ swapping the first and second halves, so `fftshift` and [`ifftshift`](@ref) are
 the same.
 
 If `dim` is not given then the signal is shifted along each dimension.
+
+The output of `fftshift` is allocated. If one desires to store the output in a preallocated array, use [`fftshift!`](@ref) instead.
 """
 fftshift
 
-function fftshift(x, dim = 1:ndims(x))
-    s = ntuple(d -> d in dim ? div(size(x,d),2) : 0, Val(ndims(x)))
-    circshift(x, s)
+fftshift(x, dim = 1:ndims(x)) = fftshift!(similar(x), x, dim)
+
+"""
+    ifftshift!(dest, src, [dim])
+
+Nonallocating version of [`ifftshift`](@ref). Stores the result of the shift of the `src` array into the `dest` array.
+"""
+function ifftshift!(dest, src, dim = 1:ndims(src))
+    s = ntuple(d -> d in dim ? -div(size(src,d),2) : 0, Val(ndims(src)))
+    circshift!(dest, src, s)
 end
 
 """
@@ -376,13 +395,12 @@ swapping the first and second halves, so [`fftshift`](@ref) and `ifftshift` are
 the same.
 
 If `dim` is not given then the signal is shifted along each dimension.
+
+The output of `ifftshift` is allocated. If one desires to store the output in a preallocated array, use [`ifftshift!`](@ref) instead.
 """
 ifftshift
 
-function ifftshift(x, dim = 1:ndims(x))
-    s = ntuple(d -> d in dim ? -div(size(x,d),2) : 0, Val(ndims(x)))
-    circshift(x, s)
-end
+ifftshift(x, dim = 1:ndims(x)) = ifftshift!(similar(x), x, dim)
 
 ##############################################################################
 

test/runtests.jl

@@ -103,20 +103,37 @@ end
     @test @inferred(AbstractFFTs.fftshift([1 2 3])) == [3 1 2]
     @test @inferred(AbstractFFTs.fftshift([1, 2, 3])) == [3, 1, 2]
     @test @inferred(AbstractFFTs.fftshift([1 2 3; 4 5 6])) == [6 4 5; 3 1 2]
+    a = [0 0 0]
+    b = [0, 0, 0]
+    c = [0 0 0; 0 0 0]
+    @test (AbstractFFTs.fftshift!(a, [1 2 3]); a == [3 1 2])
+    @test (AbstractFFTs.fftshift!(b, [1, 2, 3]); b == [3, 1, 2])
+    @test (AbstractFFTs.fftshift!(c, [1 2 3; 4 5 6]); c == [6 4 5; 3 1 2])
 
     @test @inferred(AbstractFFTs.fftshift([1 2 3; 4 5 6], 1)) == [4 5 6; 1 2 3]
     @test @inferred(AbstractFFTs.fftshift([1 2 3; 4 5 6], ())) == [1 2 3; 4 5 6]
     @test @inferred(AbstractFFTs.fftshift([1 2 3; 4 5 6], (1,2))) == [6 4 5; 3 1 2]
     @test @inferred(AbstractFFTs.fftshift([1 2 3; 4 5 6], 1:2)) == [6 4 5; 3 1 2]
+    @test (AbstractFFTs.fftshift!(c, [1 2 3; 4 5 6], 1); c == [4 5 6; 1 2 3])
+    @test (AbstractFFTs.fftshift!(c, [1 2 3; 4 5 6], ()); c == [1 2 3; 4 5 6])
+    @test (AbstractFFTs.fftshift!(c, [1 2 3; 4 5 6], (1,2)); c == [6 4 5; 3 1 2])
+    @test (AbstractFFTs.fftshift!(c, [1 2 3; 4 5 6], 1:2); c == [6 4 5; 3 1 2])
 
     @test @inferred(AbstractFFTs.ifftshift([1 2 3])) == [2 3 1]
     @test @inferred(AbstractFFTs.ifftshift([1, 2, 3])) == [2, 3, 1]
     @test @inferred(AbstractFFTs.ifftshift([1 2 3; 4 5 6])) == [5 6 4; 2 3 1]
+    @test (AbstractFFTs.ifftshift!(a, [1 2 3]); a == [2 3 1])
+    @test (AbstractFFTs.ifftshift!(b, [1, 2, 3]); b == [2, 3, 1])
+    @test (AbstractFFTs.ifftshift!(c, [1 2 3; 4 5 6]); c == [5 6 4; 2 3 1])
 
     @test @inferred(AbstractFFTs.ifftshift([1 2 3; 4 5 6], 1)) == [4 5 6; 1 2 3]
     @test @inferred(AbstractFFTs.ifftshift([1 2 3; 4 5 6], ())) == [1 2 3; 4 5 6]
     @test @inferred(AbstractFFTs.ifftshift([1 2 3; 4 5 6], (1,2))) == [5 6 4; 2 3 1]
     @test @inferred(AbstractFFTs.ifftshift([1 2 3; 4 5 6], 1:2)) == [5 6 4; 2 3 1]
+    @test (AbstractFFTs.ifftshift!(c, [1 2 3; 4 5 6], 1); c == [4 5 6; 1 2 3])
+    @test (AbstractFFTs.ifftshift!(c, [1 2 3; 4 5 6], ()); c == [1 2 3; 4 5 6])
+    @test (AbstractFFTs.ifftshift!(c, [1 2 3; 4 5 6], (1,2)); c == [5 6 4; 2 3 1])
+    @test (AbstractFFTs.ifftshift!(c, [1 2 3; 4 5 6], 1:2); c == [5 6 4; 2 3 1])
 end
 
 @testset "FFT Frequencies" begin