Merge pull request #98 from FluxML/log

GPU-ready log function

src/layers/stateless.jl

@@ -1,15 +1,17 @@
+using NNlib: log_fast
+
 # Cost functions
 
 mse(ŷ, y) = sum((ŷ .- y).^2)/length(y)
 
 crossentropy(ŷ::AbstractVecOrMat, y::AbstractVecOrMat) =
-  -sum(y .* log.(ŷ)) / size(y, 2)
+  -sum(y .* log_fast.(ŷ)) / size(y, 2)
 
 @deprecate logloss(x, y) crossentropy(x, y)
 
 function logitcrossentropy(logŷ::AbstractVecOrMat, y::AbstractVecOrMat)
   logŷ = logŷ .- maximum(logŷ, 1)
-  ypred = logŷ .- log.(sum(exp.(logŷ), 1))
+  ypred = logŷ .- log_fast.(sum(exp.(logŷ), 1))
   -sum(y .* ypred) / size(y, 2)
 end