Fix MapDataset.

Author: Oceania2018

src/TensorFlowNET.Core/Data/DatasetV2.cs

@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Tensorflow.Framework.Models;
+using static Tensorflow.Binding;
 
 namespace Tensorflow
 {
@@ -98,6 +99,20 @@ public IDatasetV2 apply_options()
             return dataset;
         }
 
+        public Tensor dataset_cardinality(string name = null)
+        {
+            if (tf.Context.executing_eagerly())
+            {
+                var results = tf.Runner.TFE_FastPathExecute(tf.Context, tf.Context.DeviceName,
+                    "DatasetCardinality", name,
+                    null,
+                    variant_tensor);
+                return results[0];
+            }
+
+            throw new NotImplementedException("");
+        }
+
         public override string ToString()
             => $"{GetType().Name} shapes: {string.Join(", ", structure.Select(x => x.shape))}, types: {string.Join(", ", structure.Select(x => "tf." + x.dtype.as_numpy_name()))}";
 
@@ -117,7 +132,9 @@ public override string ToString()
                     break;
                 }
 
-                yield return (results[0], results.Length == 1 ? null : results[1]);
+                yield return results.Length == 2
+                    ? (results[0], results[1])
+                    : (null, results[0]);
             }
         }
 

src/TensorFlowNET.Core/Data/IDatasetV2.cs

@@ -74,5 +74,7 @@ IDatasetV2 map(Func<Tensor, (Tensor, Tensor), (Tensor, Tensor)> map_func,
         /// </summary>
         /// <returns></returns>
         IDatasetV2 apply_options();
+
+        Tensor dataset_cardinality(string name = null);
     }
 }

src/TensorFlowNET.Core/Data/MapDataset.cs

@@ -15,11 +15,11 @@ public MapDataset(IDatasetV2 input_dataset,
             bool preserve_cardinality = false,
             bool use_legacy_function = false) : base(input_dataset)
         {
-            var func = new ConcreteFunction($"autograph_{map_func.Method.Name}");
-            var input = tf.placeholder(input_dataset.element_spec[0].dtype, name: "input");
+            using var func = new ConcreteFunction($"autograph_{map_func.Method.Name}");
+            var input = tf.placeholder(input_dataset.element_spec[0].dtype);
             var output = map_func(input);
             func.ToGraph(input, output);
-
+            
             structure = func.OutputStructure;
 
             variant_tensor = ops.map_dataset(input_dataset.variant_tensor,

src/TensorFlowNET.Core/Functions/ConcreteFunction.cs

@@ -130,6 +130,9 @@ ForwardBackwardCall SelectForwardAndBackwardFunctions(Tensors args, int possible
             return new ForwardBackwardCall(functions, args, tape_watching: true);
         }
 
+        public override string ToString()
+            => Name;
+
         public void Dispose()
         {
             c_api.TFE_ContextRemoveFunction(tf.Context.Handle, Name, tf.Status.Handle);

src/TensorFlowNET.Core/Keras/ArgsDefinition/TensorLikeDataAdapterArgs.cs renamed to src/TensorFlowNET.Core/Keras/ArgsDefinition/DataAdapterArgs.cs

@@ -2,10 +2,11 @@
 
 namespace Tensorflow.Keras.ArgsDefinition
 {
-    public class TensorLikeDataAdapterArgs
+    public class DataAdapterArgs
     {
         public Tensor X { get; set; }
         public Tensor Y { get; set; }
+        public IDatasetV2 Dataset { get; set; }
         public int BatchSize { get; set; } = 32;
         public int Steps { get; set; }
         public int Epochs { get; set; }

src/TensorFlowNET.Core/Keras/ArgsDefinition/DataHandlerArgs.cs

@@ -6,6 +6,7 @@ public class DataHandlerArgs
     {
         public Tensor X { get; set; }
         public Tensor Y { get; set; }
+        public IDatasetV2 Dataset { get; set; }
         public int BatchSize { get; set; } = 32;
         public int StepsPerEpoch { get; set; } = -1;
         public int InitialEpoch { get; set; } = 0;