I have some code that roughly follows this pattern where a function g
iteratively calls a function f
, stores the results in an array where the input to the next call to f
involves the output of the last call to f
, and returns the resulting array:
import Zygote
f(x, y) = sin.(x + y)
function g(x0, y, n)
xs = Array{eltype(x0)}(undef, length(x0), n)
xs[:, 1] = x0
for i = 2:n
xs[:, i] = f(xs[:, i - 1], y)
end
return xs
end
function g_zygote(x0, y, n)
xs = Zygote.Buffer(x0, length(x0), n)
xs[:, 1] = x0
for i = 2:n
xs[:, i] = f(xs[:, i - 1], y)
end
return copy(xs)
end
x0 = zeros(2)
y = zeros(2)
h(y) = sum(g(x0, y, 3))
h_zygote(y) = sum(g_zygote(x0, y, 3))
zgrad = Zygote.gradient(h_zygote, y)[1]#looks good
I can make this code differentiable with Zygote using Zygote.Buffer
(and g_zygote
, as above), but I would like to define an rrule
method for g
to make this work with ChainRules. Note that in my case, the function f
is much more complicated than the one here, but I have successfully defined the rrule
for that. Does anyone know how to define an efficient rrule
for g
?
Any help would be greatly appreciated!