Fix issue #760

Author: SanftMonster

src/TensorFlowNET.Core/Operations/gen_array_ops.cs

@@ -269,7 +269,7 @@ public static (Tensor, Tensor) unique(Tensor x, TF_DataType out_idx = TF_DataTyp
 
         public static Tensor[] unpack(Tensor value, int num, int axis = 0, string name = null)
             => tf.Context.ExecuteOp("Unpack", name, new ExecuteOpArgs(value, num)
-                    .SetAttributes(new { axis }));
+                    .SetAttributes(new { axis, num }));
 
         public static Tensor where(Tensor condition, string name = null)
         {

test/TensorFlowNET.Keras.UnitTest/Gradient.cs

@@ -0,0 +1,76 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System.Linq;
+using Tensorflow;
+using Tensorflow.Keras.Engine;
+using static Tensorflow.Binding;
+using static Tensorflow.KerasApi;
+using Tensorflow.NumPy;
+
+namespace TensorFlowNET.Keras.UnitTest;
+
+[TestClass]
+public class GradientTest
+{
+    public Model get_actor(int num_states)
+    {
+        var inputs = keras.layers.Input(shape: num_states);
+        var outputs = keras.layers.Dense(1, activation: keras.activations.Tanh).Apply(inputs);
+
+        Model model = keras.Model(inputs, outputs);
+
+        return model;
+    }
+
+    public Model get_critic(int num_states, int num_actions)
+    {
+        // State as input
+        var state_input = keras.layers.Input(shape: num_states);
+
+        // Action as input
+        var action_input = keras.layers.Input(shape: num_actions);
+
+        var concat = keras.layers.Concatenate(axis: 1).Apply(new Tensors(state_input, action_input));
+
+        var outputs = keras.layers.Dense(1).Apply(concat);
+
+        Model model = keras.Model(new Tensors(state_input, action_input), outputs);
+        model.summary();
+
+        return model;
+    }
+
+    [TestMethod]
+    public void GetGradient_Test()
+    {
+        var numStates = 3;
+        var numActions = 1;
+        var batchSize = 64;
+        var gamma = 0.99f;
+
+        var target_actor_model = get_actor(numStates);
+        var target_critic_model = get_critic(numStates, numActions);
+        var critic_model = get_critic(numStates, numActions);
+
+        Tensor state_batch = tf.convert_to_tensor(np.zeros((batchSize, numStates)), TF_DataType.TF_FLOAT);
+        Tensor action_batch = tf.convert_to_tensor(np.zeros((batchSize, numActions)), TF_DataType.TF_FLOAT);
+        Tensor reward_batch = tf.convert_to_tensor(np.zeros((batchSize, 1)), TF_DataType.TF_FLOAT);
+        Tensor next_state_batch = tf.convert_to_tensor(np.zeros((batchSize, numStates)), TF_DataType.TF_FLOAT);
+
+        using (var tape = tf.GradientTape())
+        {
+            var target_actions = target_actor_model.Apply(next_state_batch, training: true);
+            var target_critic_value = target_critic_model.Apply(new Tensors(new Tensor[] { next_state_batch, target_actions }), training: true);
+
+            var y = reward_batch + tf.multiply(gamma, target_critic_value);
+
+            var critic_value = critic_model.Apply(new Tensors(new Tensor[] { state_batch, action_batch }), training: true);
+
+            var critic_loss = math_ops.reduce_mean(math_ops.square(y - critic_value));
+
+            var critic_grad = tape.gradient(critic_loss, critic_model.TrainableVariables);
+
+            Assert.IsNotNull(critic_grad);
+            Assert.IsNotNull(critic_grad.First());
+        }
+    }
+}