_ListFetchMapper for multiple fetch in Operation and Tensor.

src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs

@@ -10,7 +10,6 @@ namespace Tensorflow
     /// </summary>
     public class _ElementFetchMapper : _FetchMapper
     {
-        private List<object> _unique_fetches = new List<object>();
         private Func<List<object>, object> _contraction_fn;
 
         public _ElementFetchMapper(object[] fetches, Func<List<object>, object> contraction_fn)
@@ -32,7 +31,7 @@ namespace Tensorflow
         /// </summary>
         /// <param name="values"></param>
         /// <returns></returns>
-        public NDArray build_results(List<object> values)
+        public override NDArray build_results(List<object> values)
         {
             NDArray result = null;
 
@@ -51,10 +50,5 @@ namespace Tensorflow
 
             return result;
         }
-
-        public List<object> unique_fetches()
-        {
-            return _unique_fetches;
-        }
     }
 }

src/TensorFlowNET.Core/Sessions/_FetchHandler.cs

@@ -10,7 +10,7 @@ namespace Tensorflow
     /// </summary>
     public class _FetchHandler
     {
-        private _ElementFetchMapper _fetch_mapper;
+        private _FetchMapper _fetch_mapper;
         private List<Tensor> _fetches = new List<Tensor>();
         private List<bool> _ops = new List<bool>();
         private List<Tensor> _final_fetches = new List<Tensor>();
@@ -18,7 +18,7 @@ namespace Tensorflow
 
         public _FetchHandler(Graph graph, object fetches, Dictionary<object, object> feeds = null, Action feed_handles = null)
         {
-            _fetch_mapper = new _FetchMapper().for_fetch(fetches);
+            _fetch_mapper = _FetchMapper.for_fetch(fetches);
             foreach(var fetch in _fetch_mapper.unique_fetches())
             {
                 switch (fetch)
@@ -58,7 +58,18 @@ namespace Tensorflow
                 {
                     var value = tensor_values[j];
                     j += 1;
-                    full_values.Add(value);
+                    switch (value.dtype.Name)
+                    {
+                        case "Int32":
+                            full_values.Add(value.Data<int>(0));
+                            break;
+                        case "Single":
+                            full_values.Add(value.Data<float>(0));
+                            break;
+                        case "Double":
+                            full_values.Add(value.Data<double>(0));
+                            break;
+                    }
                 }
                 i += 1;
             }

src/TensorFlowNET.Core/Sessions/_FetchMapper.cs

@@ -1,4 +1,5 @@
-using System;
+using NumSharp.Core;
+using System;
 using System.Collections.Generic;
 using System.Text;
 
@@ -6,14 +7,26 @@ namespace Tensorflow
 {
     public class _FetchMapper
     {
-        public _ElementFetchMapper for_fetch(object fetch)
+        protected List<object> _unique_fetches = new List<object>();
+
+        public static _FetchMapper for_fetch(object fetch)
         {
-            var fetches = new object[] { fetch };
+            var fetches = fetch.GetType().IsArray ? (object[])fetch : new object[] { fetch };
+
+            if (fetch.GetType().IsArray)
+                return new _ListFetchMapper(fetches);
+            else
+                return new _ElementFetchMapper(fetches, (List<object> fetched_vals) => fetched_vals[0]);
+        }
 
-            return new _ElementFetchMapper(fetches, (List<object> fetched_vals) =>
-            {
-                return fetched_vals[0];
-            });
+        public virtual NDArray build_results(List<object> values)
+        {
+            return values.ToArray();
+        }
+
+        public virtual List<object> unique_fetches()
+        {
+            return _unique_fetches;
         }
     }
 }

src/TensorFlowNET.Core/Sessions/_ListFetchMapper.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Tensorflow
+{
+    public class _ListFetchMapper : _FetchMapper
+    {
+        private _FetchMapper[] _mappers;
+
+        public _ListFetchMapper(object[] fetches)
+        {
+            _mappers = fetches.Select(fetch => _FetchMapper.for_fetch(fetch)).ToArray();
+            _unique_fetches.AddRange(fetches);
+        }
+    }
+}

test/TensorFlowNET.Examples/LogisticRegression.cs

@@ -40,11 +40,7 @@ namespace TensorFlowNET.Examples
             var pred = tf.nn.softmax(tf.matmul(x, W) + b); // Softmax
 
             // Minimize error using cross entropy
-            var log = tf.log(pred);
-            var mul = y * log;
-            var sum = tf.reduce_sum(mul, reduction_indices: 1);
-            var neg = -sum;
-            var cost = tf.reduce_mean(neg);
+            var cost = tf.reduce_mean(-tf.reduce_sum(y * tf.log(pred), reduction_indices: 1));
 
             // Gradient Descent
             var optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(cost);
@@ -68,14 +64,23 @@ namespace TensorFlowNET.Examples
                     {
                         var (batch_xs, batch_ys) = mnist.train.next_batch(batch_size);
                         // Run optimization op (backprop) and cost op (to get loss value)
-                        var (_, c) = sess.run(optimizer,
+                        var result = sess.run(new object[] { optimizer, cost },
                             new FeedItem(x, batch_xs),
                             new FeedItem(y, batch_ys));
 
+                        var c = (float)result[1];
                         // Compute average loss
                         avg_cost += c / total_batch;
                     }
+
+                    // Display logs per epoch step
+                    if ((epoch + 1) % display_step == 0)
+                        print($"Epoch: {(epoch + 1).ToString("D4")} cost= {avg_cost.ToString("G9")}");
                 }
+
+                print("Optimization Finished!");
+
+                // Test model
             });
         }
     }

test/TensorFlowNET.Examples/Utility/DataSet.cs

@@ -52,7 +52,28 @@ namespace TensorFlowNET.Examples.Utility
                 // Finished epoch
                 _epochs_completed += 1;
 
-                throw new NotImplementedException("next_batch");
+                // Get the rest examples in this epoch
+                var rest_num_examples = _num_examples - start;
+                var images_rest_part = _images[np.arange(start, _num_examples)];
+                var labels_rest_part = _labels[np.arange(start, _num_examples)];
+                // Shuffle the data
+                if (shuffle)
+                {
+                    var perm = np.arange(_num_examples);
+                    np.random.shuffle(perm);
+                    _images = images[perm];
+                    _labels = labels[perm];
+                }
+
+                start = 0;
+                _index_in_epoch = batch_size - rest_num_examples;
+                var end = _index_in_epoch;
+                var images_new_part = _images[np.arange(start, end)];
+                var labels_new_part = _labels[np.arange(start, end)];
+
+                /*return (np.concatenate(new float[][] { images_rest_part.Data<float>(), images_new_part.Data<float>() }, axis: 0),
+                    np.concatenate(new float[][] { labels_rest_part.Data<float>(), labels_new_part.Data<float>() }, axis: 0));*/
+                return (images_new_part, labels_new_part);
             }
             else
             {