From f5a8900ffb50b7b5fede3d3c085740c41ab595ff Mon Sep 17 00:00:00 2001
From: Mike J Innes <mike.j.innes@gmail.com>
Date: Tue, 12 May 2020 17:29:35 +0100
Subject: [PATCH] xlogy broadcast adjoint

---
 src/layers/stateless.jl | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/layers/stateless.jl b/src/layers/stateless.jl
index 860bae9b..50f64b52 100644
--- a/src/layers/stateless.jl
+++ b/src/layers/stateless.jl
@@ -288,3 +288,8 @@ CuArrays.@cufunc function xlogy(x, y)
   result = x * log(y)
   ifelse(iszero(x), zero(result), result)
 end
+
+@adjoint function broadcasted(::typeof(xlogy), x::Zygote.Numeric, y::Zygote.Numeric)
+  res = xlogy.(x, y)
+  res, Δ -> (nothing, Zygote.unbroadcast(x, xlogy.(Δ, y)), Zygote.unbroadcast(y, Δ .* x ./ y))
+end