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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| """ | ||
| @grad_from_chainrules f(args...; kwargs...) | ||
| The `@grad_from_chainrules` macro provides a way to import adjoints(rrule) defined in | ||
| ChainRules to Tracker. One must provide a method signature to import the corresponding | ||
| rrule. In the provided method signature, one should replace the types of arguments to which | ||
| one wants to take derivatives with respect with Tracker.TrackedReal and Tracker.TrackedArray | ||
| respectively. For example, we can import rrule of `f(x::Real, y::Array)`` like below: | ||
| Tracker.@grad_from_chainrules f(x::TrackedReal, y::TrackedArray) | ||
| Tracker.@grad_from_chainrules f(x::TrackedReal, y::Array) | ||
| Tracker.@grad_from_chainrules f(x::Real, y::TrackedArray) | ||
| Acceptable type annotations are `TrackedReal`, `TrackedArray`, `TrackedVector`, and | ||
| `TrackedMatrix`. These can have parameters like `TrackedArray{Float32}`. | ||
| """ | ||
| macro grad_from_chainrules(fcall) | ||
| @assert isdefined(__module__, :Tracker) "Tracker not found in module $__module__. Please load `Tracker.jl`." | ||
| Meta.isexpr(fcall, :call) && length(fcall.args) ≥ 2 || | ||
| error("`@grad_from_chainrules` has to be applied to a function signature") | ||
|
|
||
| f = fcall.args[1] | ||
| # Check if kwargs... splatting is present | ||
| kws_var = Meta.isexpr(fcall.args[2], :parameters) ? fcall.args[2].args[1].args[1] : | ||
| nothing | ||
| rem_args = Meta.isexpr(fcall.args[2], :parameters) ? fcall.args[3:end] : | ||
| fcall.args[2:end] | ||
| xs = map(rem_args) do x | ||
| Meta.isexpr(x, :(::)) || return x | ||
| length(x.args) == 1 && return :($(gensym())::$(x.args[1])) # ::T without var name | ||
| @assert length(x.args) == 2 | ||
| return :($(x.args[1])::$(x.args[2])) # x::T | ||
| end | ||
| xs_untyped = map(xs) do x | ||
| Meta.isexpr(x, :(::)) || return x | ||
| return x.args[1] | ||
| end | ||
|
|
||
| untrack_args = map(enumerate(xs)) do (i, x) | ||
| Meta.isexpr(x, :(::)) || return (x, nothing) | ||
| name, type = x.args | ||
| Meta.isexpr(type, :curly) && (type = type.args[1]) # Strip parameters from types | ||
| type in (:TrackedArray, :TrackedVector, :TrackedMatrix, :TrackedReal) || return (name, nothing) | ||
| xdata = gensym(name) | ||
| return xdata, :($(xdata) = $(Tracker.data)($(name))) | ||
| end | ||
| untrack_calls = filter(Base.Fix2(!==, nothing), last.(untrack_args)) | ||
| @assert length(untrack_calls) > 0 "No tracked arguments found." | ||
| var_names = first.(untrack_args) | ||
|
|
||
| f_sym = Meta.quot(Symbol(f)) | ||
|
|
||
| if kws_var === nothing | ||
| return esc(quote | ||
| $(f)($(xs...)) = $(Tracker.track)($(f), $(xs_untyped...)) | ||
| function Tracker._forward(::typeof($(f)), $(xs...)) | ||
| $(untrack_calls...) | ||
| y, pb_f = $(CRC.rrule)($(f), $(var_names...)) | ||
| ∇internal_generated = let pb_f = pb_f # Avoid Boxing | ||
| Δ -> return Tracker.nobacksies($(f_sym), $(__no_crctangent).(pb_f($(data)(Δ))[2:end])) | ||
| end | ||
| return y, ∇internal_generated | ||
| end | ||
| end) | ||
| end | ||
| return esc(quote | ||
| function $(f)($(xs...); $(kws_var)...) | ||
| return Tracker.track($(f), $(xs_untyped...); $(kws_var)...) | ||
| end | ||
| function Tracker._forward(::typeof($(f)), $(xs...); $(kws_var)...) | ||
| $(untrack_calls...) | ||
| y, pb_f = $(CRC.rrule)($(f), $(var_names...); $(kws_var)...) | ||
| ∇internal_generated = let pb_f = pb_f # Avoid Boxing | ||
| Δ -> Tracker.nobacksies($(f_sym), $(__no_crctangent).(pb_f($(data)(Δ))[2:end])) | ||
| end | ||
| return y, ∇internal_generated | ||
| end | ||
| end) | ||
| end | ||
|
|
||
| @inline __no_crctangent(::CRC.NoTangent) = nothing | ||
| @inline __no_crctangent(::CRC.ZeroTangent) = nothing | ||
| @inline __no_crctangent(x::CRC.AbstractThunk) = CRC.unthunk(x) | ||
| @inline __no_crctangent(x) = x |