feat(crossEntropy): crossEntropy cost function

examples/xor.hs

@@ -7,20 +7,27 @@ module Main where
   main = do
     let learning_rate = 0.5
         (iterations, epochs) = (2, 1000)
-        rnetwork = randomNetwork 0 2 [8] 1 -- two inputs, 8 nodes in a single hidden layer, 1 output
+        a = (logistic, logistic')
+        rnetwork = randomNetwork 0 2 [(8, a)] (1, a) -- two inputs, 8 nodes in a single hidden layer, 1 output
 
         inputs = [vector [0, 1], vector [1, 0], vector [1, 1], vector [0, 0]]
         labels = [vector [1], vector [1], vector [0], vector [0]]
 
+        initial_cost = zipWith crossEntropy (map (`forward` rnetwork) inputs) labels
+
         network = session inputs rnetwork labels learning_rate (iterations, epochs)
         results = map (`forward` network) inputs
         rounded = map (map round . toList) results
 
+        cost = zipWith crossEntropy (map (`forward` network) inputs) labels
+
     putStrLn "parameters: "
     putStrLn $ "- inputs: " ++ show inputs
     putStrLn $ "- labels: " ++ show labels
     putStrLn $ "- learning rate: " ++ show learning_rate
     putStrLn $ "- iterations/epochs: " ++ show (iterations, epochs)
+    putStrLn $ "- initial cost (cross-entropy): " ++ show initial_cost
     putStrLn "results: "
     putStrLn $ "- actual result: " ++ show results
     putStrLn $ "- rounded result: " ++ show rounded
+    putStrLn $ "- cost (cross-entropy): " ++ show cost