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Use type of primal output in convert in chain rules #114

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Use type of primal output in convert in chain rules #114

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18 changes: 8 additions & 10 deletions ext/AbstractFFTsChainRulesCoreExt.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -30,16 +30,15 @@ function ChainRulesCore.rrule(::typeof(rfft), x::AbstractArray{<:Real}, dims)
halfdim = first(dims)
d = size(x, halfdim)
n = size(y, halfdim)
scale = reshape(
scale = convert(typeof(y), reshape(
[i == 1 || (i == n && 2 * (i - 1) == d) ? 1 : 2 for i in 1:n],
ntuple(i -> i == first(dims) ? n : 1, Val(ndims(x))),
)
))

project_x = ChainRulesCore.ProjectTo(x)
function rfft_pullback(ȳ)
ybar = ChainRulesCore.unthunk(ȳ)
_scale = convert(typeof(ybar),scale)
x̄ = project_x(brfft(ybar ./ _scale, d, dims))
x̄ = project_x(brfft(ybar ./ scale, d, dims))
return ChainRulesCore.NoTangent(), x̄, ChainRulesCore.NoTangent()
end
return y, rfft_pullback
Expand Down Expand Up @@ -74,16 +73,15 @@ function ChainRulesCore.rrule(::typeof(irfft), x::AbstractArray, d::Int, dims)
n = size(x, halfdim)
invN = AbstractFFTs.normalization(y, dims)
twoinvN = 2 * invN
scale = reshape(
scale = convert(typeof(y), reshape(
[i == 1 || (i == n && 2 * (i - 1) == d) ? invN : twoinvN for i in 1:n],
ntuple(i -> i == first(dims) ? n : 1, Val(ndims(x))),
)
))

project_x = ChainRulesCore.ProjectTo(x)
function irfft_pullback(ȳ)
ybar = ChainRulesCore.unthunk(ȳ)
_scale = convert(typeof(ybar),scale)
x̄ = project_x(_scale .* rfft(real.(ybar), dims))
x̄ = project_x(scale .* rfft(real.(ybar), dims))
return ChainRulesCore.NoTangent(), x̄, ChainRulesCore.NoTangent(), ChainRulesCore.NoTangent()
end
return y, irfft_pullback
Expand Down Expand Up @@ -115,10 +113,10 @@ function ChainRulesCore.rrule(::typeof(brfft), x::AbstractArray, d::Int, dims)
# compute scaling factors
halfdim = first(dims)
n = size(x, halfdim)
scale = reshape(
scale = convert(typeof(y), reshape(
[i == 1 || (i == n && 2 * (i - 1) == d) ? 1 : 2 for i in 1:n],
ntuple(i -> i == first(dims) ? n : 1, Val(ndims(x))),
)
))

project_x = ChainRulesCore.ProjectTo(x)
function brfft_pullback(ȳ)
Expand Down
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