Added new loss functions.

src/layers/stateless.jl

@@ -54,3 +54,31 @@ function normalise(x::AbstractArray, dims)
   Base.depwarn("`normalise(x::AbstractArray, dims)` is deprecated, use `normalise(a, dims=dims)` instead.", :normalise)
   normalise(x, dims = dims)
 end
+
+"""
+    Kullback Leibler Divergence(KL Divergence)
+KLDivergence is a measure of how much one probability distribution is different from the other.
+It is always non-negative and zero only when both the distributions are equal everywhere.
+
+"""
+function KLDivergence(ŷ, y)
+  entropy = sum(y .* log.(y)) *1 //size(y,2)
+  cross_entropy = crossentropy(ŷ, y)
+  return entropy + cross_entropy
+end
+
+"""
+    Poisson Loss function
+Poisson loss function is a measure of how the predicted distribution diverges from the expected distribution.
+
+"""
+Poisson(ŷ, y) = sum(ŷ .- y .* log.(ŷ)) *1 // size(y,2)
+
+"""
+    Logcosh Loss function
+"""
+
+logcosh(ŷ, y) = sum(log.(cosh.(ŷ .- y)))
+
+Hinge(ŷ, y) = sum(max.(0.0, 1 .-  ŷ .* y)) *1 // size(y,2)
+