make Maxout trainable

src/layers/basic.jl

@@ -167,6 +167,8 @@ function Maxout(f, n_alts)
   return Maxout(over)
 end
 
+@treelike Maxout
+
 function (mo::Maxout)(input::AbstractArray)
     mapreduce(f -> f(input), (acc, out) -> max.(acc, out), mo.over)
 end

test/layers/basic.jl

@@ -53,5 +53,11 @@ using Test, Random
             target = [0.5, 0.7].*input
             @test mo(input) == target
         end
+
+        @testset "params" begin
+            mo = Maxout(()->Dense(32, 64), 4)
+            ps = params(mo)
+            @test length(ps) == 8  #4 alts, each with weight and bias
+        end
     end
 end